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Comprehensive Description

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Description

"Nematocarcinus lanceopes, n. sp. (PL CXXXL).

 

Rostrum projecting anteriorly, nearly as long as the carapace, armed on the upper surface with a series of very small teeth, about twenty-six in number, and on the lower with eight teeth and no fringe of cilia.

 

Ophthalmopoda short and embayed in a deep orbital notch, which is armed at the outer angle with a sharp antennal tooth.

 

First pair of antennæ having the peduncle about half the length of the rostrum; first joint excavate to receive the ophthalmopoda and the other two short and cylindrical; the flagella are long and slender, the outer being a little larger at the base than the inner.

 

Second pair of antennæ carrying a scaphocerite that is nearly as long as the rostrum, and a long and slender flagellum.

 

Second pair of gnathopoda terminating in a long spatuliform joint.

 

First two pairs of pereiopoda chelate, the propodos being rather less than half the length of the carpos, which corresponds in length with the meros and ischium combined. Two succeeding pairs of pereiopoda missing. Posterior pair long, and terminating in a short, broad, and lanceolate dactylos, which articulates with the propodos in the centre of a cup-shaped hollow fringed with long hairs; the propodos is short and cylindrical, but four times as long as the dactylos; the carpos is long and cylindrical, being about twelve times as long as the propodos and a little longer than the meros, which is not armed with a prominent tooth at the carpal extremity, but is sparsely fringed with spine-like teeth on the posterior margin, and is connected with the ischium by an overlapping articulation. All the pereiopoda, excepting the last pair, carry a basecphysis, and also a rudimentary mastigobranchial plate.

 

Telson subequal with the outer plate of the rhipidura, dorsally fiat, smooth, and fringed with a few hairs at the extremity, and short spinules on the latero-dorsal angle.

 

Female Male

 

Length, entire, . . . 106mm (4.1in) 90mm (3.5in)

 

Length of carapace, . . . 31mm 25mm

 

Length of rostrum, . . . 25mm 24mm

 

Length of pleon, . . . 75mm 65mm

 

Length of third somite of pleon, . 12mm 12mm

 

Length of sixth somite of pleon, . 19mm 16mm

 

Length of telson, . . . 21mm 18mm


Habitat.— Station 152, February 11, 1874; lat. 60° 52' S., long. 80° 20' E.; Antarctic Sea; depth, 1260 fathoms; bottom, Diatom ooze. Three specimens; one male, two females. Associated with Pentacheles. Trawled.

 

This species was originally named from a belief that the posterior three pairs of legs terminated in a dactylos that was short and lanceolate in form, but the specimens are damaged, and although in my original notes I have recorded the three pairs as being so shaped, my drawing represents only two. I think that there is a possible error in the description, inasmuch as I had not at the time observed that the posterior pair in many and probably all species is rudimentary, so as to make it a distinction of generic value. The dactylos in this pair is short, broad, and lost among a mass of stiff hairs that fringe the distal margin of the propodos; it is lanceolate in form, but whether the preceding two are so or not I cannot determine.

 

The females were laden with ova of an oval form, and much larger than those of other species in which eggs have been observed. The pereiopoda that are preserved attached are not quite so long proportionately as in some other species, a circumstance that is due to the carpos being not quite so long in relation to the meros to which it is attached. The third somite of the pleon is slightly arcuate at the posterior portion, and the telson is slightly longer than in some species. Most of the other features are only of generic value and unimportant in the determination of species."

 

(Bate, 1888)

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© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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