306 MK. E. A. SMITH ON THE 



nate than at the opposite extremity, which is broadly arcuate ; 

 lower margin regularly widely arcuate. Lines of growth very 

 fine. 

 Length 6 milllm., width 6. 



Hal). Penrith, New South Wales (Mac GilHvra?/, Voyage of the 

 'Sattlesnake '). 



This species is less narrow and acuminated anteriorly than 

 S. translucidum, and not truncated at the hinder end. It is more 

 ovate and less oblique than S. qiieenslandicum. 



Genus Pisidium. 



135. Pisidium attstrale, Lamarck, var. 



Cyclas australis, Lamk. Anim. s. Vert. vol. v. p. 560; Deshayes, ed. 2, 



vol. vi. p. 270 ; id. Cat. Corbiculidce Brit. Mus. p. 285 (as Pisum). 

 Bah. Port King George, New Holland. 



The typical form of this species is said by Lamarck to come 

 from the island of Timor, Hence it seems most probable that 

 what he considered a variety from Australia is in fact a distinct 

 species. Carpenter*, on the authority of Gray, quotes Lamarck's 

 species as synonymous with Lasea rubra, Montagu. It has been 

 confused with the Gyrena australis of Deshayes by Prime ; but 

 that species is a Corhicula and synonymous with O. nepeanensis, 

 as I have already shown. 



136. Pisidium semen, Menhe. 



Pisidium semen, Menke, Moll. Nov. Roll. p. 40 ; Deshayes, Cat. Corbi^ 

 culidce in Brit. Mus. p. 284 (as Pisum) ; Prime, Appendix, Am. J. Conch. 

 v. p. 173. 

 Sab. On the sand-bank of Swan Eiver. 



This species, only a little more than a line in length, is described 

 by Menke as obliquely ovate, ventricose, with turgid umbones, 

 clothed with a yellow corneous epidermis, paler at the margin, 

 very finely transversely striated, and, when decorticated, white or 

 lilac. 



137. Pisidium Etiieridgii, n. sp. (Plate VII. fig. 35.) 



Shell slightly inequilateral, a little oblique, subcordiform, tumid, 



whitish, covered with a greyish cuticle ; anterior end the longer, 



acuminated and sharply curved ; posterior broadly rounded. Ventral 



margin regularly curved. Umbones rather prominent, with the 



* 'MazatlanCat'p. 108. 



