84 TETHYS-WEST AMERICAN. 



calloused, but with no reflexed margin over the tip. Sinus short 

 and very concave, margined. Surface smooth. Calcareous layer 

 coextensive with the excessively thin, hardly apparent cuticle. 



Length 8J, breadth 6 mill. 



St. Thomas (A. H. Riise ; Dr. Hornbeck) ; St. Vincent (Guild- 

 ing)- 



Aplysia parvula GUILDING MS. in MORCH, Journal de Conchyli- 

 ologie, 1863, p. 22; Mai. Bl. xxii, p. 176. ?J. rosea Rathke*- 

 SOWB., Conch. Icon. f. 23 (1869). 



I have given Morch's very poor descriptions of the soft parts of 

 this species, and have diagnosed and figured the shell from part of 

 the original specimens received from Morch. It is unquestionably 

 a distinct species, not closely allied to any other of the region. The- 

 shell is convex and solid, somewhat like Crepidula convexa Say in 

 contour. The large oval orifice in the mantle is also a valuable 

 distinguishing character, other described Antillean forms having 

 this foramen minute or tubular. 



Whether the parvula of Morch is really Guilding's mss. species i& 

 by no means certain ; but fortunately there is no necessity for rais- 

 ing the question. Sowerby has figured a shell from St. Vincent 

 under the name A. rosea Rathke, which is the A. parvula of Guild- 

 ing, according to him ; but the real A. rosea was a Scandinavian 

 species and in all reasonable probability a young punctata Cuv. 



III. Species of the West Coast of the Americas. 



a. Shell normal, with no accessory plate at the apex. 

 b. Swimming lobes broadly united behind. 



c. Mantle excised behind, but with no tongue-like lobe. 



d. Mantle with a submedian perforation. Black, nigra. 

 dd. Mantle with a large submedian oval orifice. Black- 

 ish, rangiana. 

 cc. Mantle with a submedian perforation, and a posterior 

 long, tongue-like siphonal lobe. Violet, with some white 

 spots, blackish in alcohol, inca 

 bb. Swimming lobes free to their union with foot behind. 



c. Mantle with a subcentral tube or papilla ; swimming 

 lobes very ample. 

 d. Maculated ; opaline gland with one orifice, 



chierchiana^ 



