384 APPENDIX. 



side ; from it there runs a strait rib or process continued 

 nearly to tlie outer margin, and indicated externally by a 

 depression or groove. 



Animal ample, provided Avitli four very long and rather 

 broad linear rugose (or ciliated ?) tentacula ; mantle pro- 

 duced into a long siphon ; foot ver}^ large, expanded, trun- 

 cate in front, bearing the operculum near its posterior 

 extremity, but not accompanied by filamentous processes 

 or lobes. A float, (Miis. Brit, and Geol.) 



This very remarkable mollusk was taken in the towing 

 net off Cape Byron, on the east coast of Austraha, in Lat. 

 28° 40' S., fifteen miles from the shore. It was floating 

 and was apparently gregarious. Mr. Macgilhvray states 

 that it is fru^nished with a float in the manner of lanthina. 

 The largest specimens measure rather less than two lines 

 in diameter. The shell is of a yellow horn colour (as is 

 also the operculum), thin and transparent. It bears a 

 striking resemblance to our much more minute Jeffreysia 

 opalina. The four tentacula and the form of the very 

 peculiar operculum also seem to indicate considerable 

 affinity with the genus Jeffreysia of Alder, and an ex- 

 amination of the remains of the tongue extracted from a 

 dried specimen shewed an arrangement and form of the 

 lingual denticles very closely resembling that exhibited by 

 Jeffreysia. On the other hand, the very distinct and long 

 siphonal tube delineated in Mr. Macgillivray's drawing, 

 taken when the animal was ahve, would seem to refer this 

 genus to some family probably near to CancellaridcB. It 

 is certainly entirely distinct in every respect from any 

 known Gasteropod. It is a form of \evj great interest to 

 the geologist, for in it we see the nearest representation of 

 certain palaeozoic (especially Lower Silurian) univalves 

 hitherto referred to Littorina, but wliich, judging from 

 their associates and the indications aflbrded bv the strata 



