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Comprehensive Description

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General Description

The integument is thin, shining and minutely puncatate. The rostrum is almost straight to slightly upturned in the distal half. A sharply pointed tip reaches the proximal part of the third peduncular article of the antennule. The dorsal margin is raised into a thin serrate crest containing 17 - 21 teeth varying from obliquely erect in the proximal part to nearly horizontal, shorter and more distant distally. About one-third of the length of the crest continues onto the carapace. The ventral margin is much less prominent and armed with a row of 6 correspondingly smaller subterminal teeth, that are sometimes obscure. Lateral carina is broadened proximally and confluent with the orbital margin. The carapace is broad based but slender, with an acuminate antennal spine. The pterygostomian spine is correspondingly acuminate and prominent. A prominent anterior antennal carina curves posteroventrally to intersect obliquely with the carina extending from the pterygostomian spine at about the midlength of the carapace, with an associated groove continuing indistinctly posteriad.

The abdomen of both males and females is broadly arched dorsally, and gradually tapers distally. The narrowest part of the sixth somite is less than two-thirds the width of the first somite. The pleura of the 3 anterior somites are broadly rounded, with the margin of the third slightly serrated. The margin of the fourth somite is drawn posterolaterally to a strong spine flanked dorsally by 0 – 3 more slender and smaller spines and preceded on the ventral margin by 0 – 2 small spines. The number, position and shape of either the lateral or ventral spines may be asymmetrical. The posterolateral corner of the fifth pleura is acuminate and flanked dorsally by 1 or 2 spines analogous to those on somite 4. The sixth somite has a middorsal length about 1.7 times that of the fifth. A broad-based midlateral spine overlaps the base of the telson, and a smaller posterolateral spine is acute. The fourth and fifth somites each have a strong, posteriorly directed spine on the sternite. The telson is elongate and subrectangular, with a length about 3.0 times the anterior width, 6.8 times the posterior width, and ca. 1.4 times the length of the sixth somite (not including the posterior spines). The telson has 7 dorsolateral spines of nearly uniform size. The posterior margin is convex, and armed with 2 principal spines at each corner and 10 or 11 feathered strong setae on the distal margin between the spines.

The eyes have an imperfectly developed cornea that is unfaceted though diffusely pigmented. The eyes are ovate in outline, though fused to each other mesially, and each with a short upturned spine on the anterior surface.

The antennular peduncle reaches beyond the end of the antennal scale. The basal article is 1.1 as long as the second and about 2.5 as long as the third, all measured on the ventral margin. The stylocerite is well separated from the peduncle, tapering to a slender elongate tip that reaches the tip of the distolateral spine of the basal article. The latter exceeds the distodorsal margin of the article, and is fringed by a transverse subdistal row of setae and closely appressed to the second article, with a distomesial spine that is much shorter. A shorter second article has a stronger mesiodistal spine. The dorsolateral flagellum are ca. the length of the carapace and thickened in the basal two-thirds. There are annulations on the flagellum, except at the base, which are longer in the female than the male, and much longer in the female in the whiplike distal part. The ventromesial flagellum are somewhat shorter and with annulations of a variable but shorter length.

The antennal scale is ca. twice as long as wide, with a strong distolateral tooth, falling slightly short of the broadly rounded distal margin of the blade. The basal article has an acute distal spine ventrally. The flagellum slightly exceeds the length of the body.

The mandibles are similar, with a 2-segmented palp, a broad incisor process armed with 8 marginal teeth, and a slender simple molar process that is divergent, with a narrowly rounded tip that is minutely setose.

The first maxilla has a proximal endite that is asymmetrically oval-triangular, with a distal margin that bears many long setae. The distal endite has a narrow base but is broadened distally, armed with ca. 30 short spines on the mesial margin and with scattered longer spinules submarginally and marginally beyond either end of the spine row. The palp is scarcely bifurcated, with a long distal spine on an obsolescent proximomesial branch and one shorter submarginal spine on the distal branch.

The second maxilla has a proximal endite represented by 2 similar lobes. The distal endite is subtriangulr, expanded mesiodistally and paralleled laterally by a narrow, somewhat twisted palp. The scaphognathite has an anterior lobe that is rectangulo-ovate which is fringed with uniformly long, silky setae on the anterior and mesial borders and uniformly shorter setae along the entire lateral margin. The posterior lobe is narrow and acuminate, fringed on the blunt tip and adjacent mesial margin by strikingly long, strong, tangled setae preceded proximally by shorter setae similar to those on the lateral margin.

The first maxilliped has an irregularly fusiform endite, a short palp that is concealed and greatly exceeded in length and size by a leaf-like exopod. The epipod is obscurely bilobed. An indistinct mesial lobule on the exopod possibly resents the incipient lash.

The second maxilliped is somewhat pediform but is flattened, with the mesial margin of the articles bearing long, feathered setae. The mesial surface of the terminal article is densely setose, with the exopod barely exceeding the leaf-like epipod.

The third maxilliped is slender and 5 segmented, reaching beyond the antennular peduncle. The terminal article is trigonal in cross section and tapers distally, bearing 3 spines and transverse tracts of dense setae along the mesial surface. A similar tract of setae occurs on the carpus and another conspicuous group are located mesiodistally on the merus-ischium. The merus-ischium has a stout distolateral spine at the articulation with the carpus. The exopod is much reduced, subtriangular, and without a lash.

The first pereopods are chelate, subequal and sexually dimorphic in fully mature individuals. The fingers are curved ventrally and slightly laterad. The level of the tip of the dactylus is slightly shorter or equal to that of the fixed finger. The dactylus is more slender than the fixed finger. The mesial surface of each finger is convex, and the lateral surface is concave with opposed surfaces uniformly offset. The fingers close without a gape, each armed on the prehensile edge with a row of almost uniform teeth so closely set as to be almost contiguous. The acute tip of the dactyl is slightly spooned by elongate teeth slanted distad and curving around its external edge. There is a line of sensory hairs mesial to the cutting edges. The leg is shorter than or almost equal to the third maxilliped. The palm of the male is inflated laterally, but is somewhat irregularly concave mesially, with a length 1.4 times the greatest height and longer than the fingers. The palm is relatively shorter in the female, 0.3 times the length of the fingers. The carpus is shorter than the palm, with an oblique ventral crest that ends in a strong distolateral spine, flanked mesially by a patch of setae on a polygonal raised area. The merus is somewhat swollen in the distal half, distinct from the ischium but fused to it. Neither are armed.

The second pereopod is shorter and more slender than the first, reaching to about the end of the antennal penduncle. The fingers are slightly longer than the palm and similar in size and shape, with the opposed edges lacking a gape. Each pectinate has a single row of teeth in the distal half directed obliquely distad and increasing slightly in size to end in a noticeably stronger tooth that crosses the opposite member when closed, but spineless proximally. The carpus is slender, about 1.16 times longer than the chela. The merus and ishium are unarmed.

The third to fifth pereopods are similar in length and structure, the third reaching to or slightly beyond the tip of the antennal scale. Each short dactyl is armed with about 4 - 6 corneous spines on flexor surface, grading from small proximally to the longest and strongest distally. The carpus of each has a distodorsal extension projecting as a stop along the proximal part of the propodal extensor surface. The third leg is stronger, at least in the merus-ischium, than the fourth or fifth. The propodus is successively longer from the third to fifth leg. The merus of each has a ventral spine at one-third and two-third length. The ischium of the third, fourth and fifth legs have two spines in line with those on the merus.

The pleopods are well developed. The first pairs have endopods about half the length of the exopods in both sexes, narrowed into a distomesial projection in the male, but evenly tapering in the female. The appendix masculia of the second pair in males is armed with 7 slender spines that extend beyond the level of the simple slender appendix interna. The endopods of the third to fifth in the male and second to fifth in the female have a simple slender appendix interna, but that of the fifth is blunt tipped.

The uropod has rami subequal in length, with the lateral ramus slightly exceeding the distal end of the telson, and with a moveable spine mesial to a smaller distolateral tooth. The diaeresis is sinuous.

(Williams, 1988)

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