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Species in the genus Pterotrachea have elongate and mostly cylindrical bodies, with the result that they are the most streamlined of the three heteropod families. The proboscis is slender, elongate and highly mobile, and terminates in a small buccal mass (in contrast with that in carinariids). The trunk is elongate and the cutis anterior to the swimming fin is thickened either ventro-laterally to form gelatinous folds (bib) or expanded laterally as an oval, cuticular disk. The tail is large and laterally compressed, which aids in burst swimming (resulting from side-to-side flexion of the trunk and tail). This swimming mode contrasts with the normal slower swimming mode, involving only the swimming fin. The tail terminates in two small, leaf-like lobes and, emerging from between the lobes, a filamentous extension, that may or may not be present. The larval shell is cast off following metamorphosis. A small sucker on the swimming fin is present only in males.
A genus in the family Pterotracheidae with the following characteristics:
- Body streamlined; elongate and basically cylindrical in shape
- Proboscis slender, with a small buccal mass, and is highly mobile
- Cutis thickened ventro-laterally or laterally on the anterior part of the trunk, forming either a bib or an cuticular disk, respectively
- Tail large and laterally flattened, aiding in burst swimming involving side-to-side body flexion
- Swimming fin sucker present only in males