NATURAL SCIENCES OF PHILADELPHIA. 485 



26. E. plicatilis, Deshayes, sp. 



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

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



Description. " R. testa elongato-ovata, tenui, fragili, pellucida, compres- 

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

 tudinem testae aequante, inferne sensini attenuate ; valvis in tres areas divisis, 

 una anticii lata, transversim regulariter striata, striis tenuissimis, oblique sub- 

 lente striolatis, parte secunda oblique mediana, angusta, laevigata, postica, 

 pyramidata, prominentiore, sulcis depressiusculis circumdata, transversim 

 profunda sulcata, quasi scalariformi, area circa, ligamentum planulata, elongato 

 lanceolata, ligamento crasso, elongato." Deshayes. 



Hob. Pbilippines, Zebu. Coll. Cuming. 



27. R. rostrata,* Spengler, sp. 



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

 Gastrochaena 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 Mans, (partim,) Chemnitz, x. f. 1680 'SI, 1788. 

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

 area anali longitudinali pyramidata, externe sulcata, plicis transversis rectis 

 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. truncata 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 umbones is wide, and not acumi- 

 nate as in R. truncata. 



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

 D'Orbigny, by the "cotes anales plus droites, son sillon lateral bien 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. 



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



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

 Hanley, Desc. Cat. p. 10, t. 9, f. 40, 1842. 

 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- 

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

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

 Hab. 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. 



1861.] 



