53 



26. R. plicatilis, Deshayes, sp. 



Gastrochsena plicatilis, Deshayes, Zool. Proc. Lond. p. 329, 1854 

 Rocellaria plicatilis, H. and A. Adams, Genera, ii. p. 336, 1856. 



Description.—' 1 R. testa elongato-ovata, tenui, i'ragili, pellucida, compres- 

 siuscula, longe hiante, postice truncata, hiatu mazimo, elongato, totam alti- 

 tudineiu testse sequante, inferno sensim attenuate ; valvis in tres areas divisis, 

 una antica lata, transversim regulariter striata, striis tenuissiniis, oblique sub- 

 lente striolatis, parte secunda oblique inediana, angusta, laevigata, postioa 

 pyrauiidata, prominentiore, sulcis depressiusculis circurndata, transversim 

 profunde sulcata, quasi scalariforrni, area circa ligauientum planulata, elongato 

 lanceolata, ligamento crasso, elongato." — Deshayes. 



Hub. — Philippines, Zebu. Coll. Cuming. 



27. R. r o s t r a t a , * Spengler, sp. 



Gastrochsena rostrata, Spengler, Nov. Act. Sc. Soc. ii. 1783. 

 Gastrochsena callosa, Philippi, Weigmann's Archiv, 1845. 

 Gastrochsena Chemnitziana, D'Orbigny, Sagra's Cuba, Moll. p. 229, t. 29, 



f. 29, 30. 

 Beau, Cat. Coq. Guadaloupe, p. 27, 1858. 

 Rocellaria rostrata, Morch, Catalogue, 1853. 



H. and A. Adams, Genera, ii. p. 336, 1856. 

 Pholas bians, (partim,) Chemnitz, x. f. 1680--' 81, 1788. 

 Description. — " R. testa oblongo-cuneata, tenui, albida, concentrice. striata, 

 area, anali longitudinali pyrauiidata, externe sulcata, plicis transyersis reetis 

 ornata ; latere anali elongata, transversim truncato ; latere buccali angustato, 

 obtuso; hiatu magno. Long. 24 mill."— D'Orbigny. 

 Hub. — West Indies. 



This species is distinguished from R. t r u n c a t a by its large transverse 

 lamellar ribs, their place being occupied in the latter species by coarse striae, 

 The anterior margin of R. r o s t r a t a is also more convex and not emarginate- 

 and the portion of the shell anterior to the umboues is wide, and not acumi- 

 nate as in R. t r u n c a t a . 



It resembles R. mytiloides, but maybe distinguished, according to 

 D'Orbigny, by the " cites anales plus droites, son sillon lateral bi en plus pro- 

 nonce, et ses stries plus regulieres.'''' The specimens of the two species in the 

 collection of the Academy, though authentic, do not exhibit sufficient dis- 

 tinctive characters to clear the mind from all doubt, though the probability is 

 that they are properly separated. 



28. R. truncata,* Sowerby, sp. 



Gastrochsena truncata, Sowerby, Zool. Proc. Lond. p. 21, 1834. 

 Th. Midler, Syn. Test. Viv. p. 235, 1836. 

 Hanley, Desc. Cat. p. 10, t. 9, f. 40, 1S42. 

 Catlow, Conch. Nomenc. p. 2, 1845. 

 Jay, Catalogue, 4th edit. 1850. 

 Carpenter, Mazatlan Shells, Brit. Mus. Cat. p. 14, 

 1857. 

 Rocellaria truncata, II. and A. Adams, Genera, ii. p. 336, 1856. 

 Description. — " R. testa oblonga, postice rotundato-truncata, striata, sor- 

 didc albicante ; epidermide tenui lamellosa, postice tecta, ; latere antico bre- 

 vissimo, subacuminato. Long. 1-4, lat. 0-7, alt. 0-7, poll."— Sowerby. 

 Eab. — In Sinu Panamensi, (Isle of Perico.) Found in Spondyli. 

 This is a very distinct species, and is well authenticated both by the nume- 

 rous specimens existing in cabinets, and by Mr. Carpenter's excellent descrip- 

 tion. The original diagnosis by Sowerby is rather meagre, though much 

 better than several others by this author. The hinge is armed with a distinct 

 spathulate lamina. 



