496 



concentrice striata, extremitate plus minusve attenuata; laminis 

 tribus, quarum una elongata ad margines ventrales, una inter 

 margines dorsales, una super umbones parva, subquadrata. 



Resembling Ph. striata, but having the dorsal shield very small, 

 and of an oblong square, somewhat rounded anteriorly. The 

 specimens, having bored in floating mahogany, have taken a 

 reddish colour. 



33. Pholas rivicola (pi. cviii. f. 90, 91), Soiverbg, junr., 

 Pro. Zool. Soc, 1849. 



Ph. testa clausa, cuneiformi, transverse canali divisa ; parte an- 

 tica. oblique dimidiata, latere dorsali striato, latere ventrali lsevi, 

 subangulato ; parte postica subelongata, lajvi, epidermide laminis 

 angulatis marginibus serratis ornata ; lamina dorsali subquadrata, 

 in medio longitudinaliter divisa. 



A cuneiform, enclosed species, divided transversely by a canal ; 

 the dorsal side of the anterior obliquely striated ; the posterior is 

 attenuated, and covered by a dark olive-green epidermis, which is 

 thrown out at regular intervals in angular fringed laminae. This 

 is the only Pholas yet found inhabiting fresh water. The fringes 

 of the epidermis, and the divided dorsal shield, render it perfectly 

 distinct. For this species I am indebted to the courtesy of A. 

 Adams, Esq., Surgeon of the ship Samarang, who collected it at 

 a place called Gunny Taboor, twelve miles up the Pantai river, 

 where the water was perfectly fresh, and where it burrowed in 

 considerable numbers in the floating piles which had been long 

 used as a landing pier. 



34. Pholas obtecta (pi. cviii. f. SO, 81), Sowerby, junr., 

 Pro. Zool. Soc, 1849. 



Ph. testa ovata, subpyriformi, clausa, canali transverse dimi- 

 diata ; parte antica latere dorsali minute striato, latere ventrali lsevi, 

 rotundo ; parte postica kevi, ad margines laminis duabus protecta, 

 ad terminum laminis duplicatis cyathiformibus producta; ad um- 

 bones lamina testacea, postice bilobata, antice late versus marginem 

 ventralem expansa. 



A rather ovate shell, rounded anteriorly, and attenuated poste- 

 riorly. It is divided by a grove, and the anterior part is closed by 

 an expansion of the margins; posteriorly, the dorsal and ventral 

 edges are covered by a folded membrane, and at the end there is a 

 narrow, fiattish, cup-shaped expansion divided laterally. The um- 

 bones are covered by a shelly case, which reaches in two lobes 



