LEPAS AUSTRALIS. 89 



— in one specimen having the mandible on one side 

 bearing only four teeth, — and in the frequent absence of 

 filamentary appendages, there is some approach to the 

 genus Ptecilasma ; but there is no such approach in the 

 characters derived from the capitulum. We have seen 

 that, as in so many other species of this genus, most 

 of the parts are variable, and this is the case to a most 

 unusual extent in the form of the maxillae. Dr. Leach 

 has attached eight specific names to the specimens 

 preserved in the British Museum. 



5. LEPAS AUSTRALIS. PL I, fig. 5. 



L. valvisglabris, tenuibus^fragilibus ; scutorum dentibus 

 umbonalibus utrinque internis ; carina parte superior e 

 lata, plana, supra fur cam valde constrictd ; fur cm cruribus 

 latis, plants, tenuibus, acuminatis, intermedio margine 

 non reflexo. 



Valves smooth, thin, brittle; scuta with internal um- 

 bonal teeth on both sides. Carina with the upper part 

 broad, flat ; much constricted above the fork, which has 

 wide, flat, thin, pointed prongs, with the intermediate 

 rim not reflexed. 



Filaments, two on each side. 



Common on Laminariae in the whole Antarctic Ocean : Bass's Straits, 

 Van Diemen's Land : Bay of Islands, New Zealand, lat. 35° S. : lat. 

 50° S., 172° W. : coast of Patagonia, lat. 45° S. : attached to bottom of 

 H. M. S. Beagle, lat. 50° S., Patagonia: attached to a Nullipora, (I presume 

 a drift piece,) British Museum. 



General Appearance. — Capitulum rather obtuse and 

 thick; valves thin, brittle, approximate, either white 

 and transparent, or dirty -brown and opaque ; or some- 

 times tinted internally with purple (perhaps the effects of 

 being preserved in spirits) ; surface plainly marked by 

 lines of growth, rarely marked with traces of lines radiat- 

 ing from the umbones. Scuta with teeth on both sides, 



i 

 4 *^m~ 



