204 Mr. J. C. Melvill on 



only tinged towards the umbones with rose, while others are 

 whitish, and a third flesh-colour. 



Specimens exist, unnamed, in the British Museum. 



Gari amianta * , sp. n. (PI. XII. fig. 12.) 



6?. testa oblonga, sequivalvi, fere {©quilaterali, tenui; valvis utrinque 

 hiulcis, albidis, nitidis, superficie irregulariter concentrice striata, 

 striis rudibus, sed teniiibus ; umbonibus prominulis, approximatis, 

 reetis ; ruargine dorsali postice paullulnm excavato, antice leuiter 

 declivi, prolongato, ventrali fere recto ; intus albescente. nitido, 

 linea palliali apud medium extensa, profunde sinuosa ; cardine 

 valvse sinistrse dente uno simplici, dextrse dente bifido prsedito. 



Alt. 18, lat. 28, diam. 5 mm. 



A pure white shell, equivalve and almost equilateral, thin, 

 in form showing some affinity to certain PsammotellcB, e. g. 

 BiippeUiafia, Reeve, from the Red Sea, but possessing no 

 callosity of the hinge-margin and no trace of violet colour. 

 The surface of the valves is finely but rudely and irregularly 

 concentrically striate, the umbones are approximate, promi- 

 nent ; dorsal margin slightly excavate on the posterior side, 

 which is prolonged, and on the anterior more gradually 

 sloping, the ventral margin being straight. The valves gape 

 both posteriorly and anteriorly ; the hinge of the left valve 

 has one simple tooth, which is bifid in the right valve. 

 "Within, the surface is white, shining, the pallial line deeply 

 sinuous and extending to the middle of each valve. 



Petricola lyra^ sp. n. (PI. XII. fig. 13.) 



P. testa insequilaterali, rudi, albida, tenui ; umbonibus niveis, politis ; 

 valvis tumidulis, parum hiantibus, extus irregulariter radiatim 

 costatis, costis acutis, carinulatis, apud medium distortis vel 

 deviis ; postica carina magna, acuta, interstitiis transversim rudi- 

 liratis, liris remotis, antice rotundata, margine ventrali convexi- 

 usculo ; intus alba, nitida ; impressione musculari postica rotunda, 

 magna, cardinibus tridentatis, linea palliali conspicua, sinuosa. 

 t. 12, lat. 15, diam. 7 mm. 



A Petricola with a certain attempt at regularity of outline 

 and symmetry of ten radiate, acutely keeled, ribs, the last 

 rib on the posterior side being in both valves especially 

 conspicuous and well defined, while the anterior ribs are more 

 distant. Concentrically the surface is remotely Urate, the 



* dfiiavTos, pure, unsullied. 



