On neiu Shells from Mauritius arid California. 2-55 



XXXIX. — Descriptions of new Species of SJulls from 

 Mauritius and Calijornia. \^y EdgaU A. Smitii. 



Pecten CroucJii. 



Testa compressa, iiifoi-nc rotundata, ad apiccm peracurainala, sub- 

 aeqiiivalvis, costis validis octo in utraque valva instructa, supra 

 et iiifor costas radiatiin striata, undicjiie microscopico suporficial- 

 itor reticulata ; valva sinistra albida, aurantio vel purpureo plus 

 minus tincta, supra et inter costas saturate purpureo vel san- 

 guineo irregulariter copiose maculata, lineisque angulatis albis 

 inter costas hie illic oriiata ; valva dextra pallidior, marginem 

 ventralcm versus aurantio vel purpureo tiiicta, inter et -supra 

 costas parum maculata ; margo cardinis perobliijuus, rectilinearis, 

 valde iiKcqualis, parte postica brevissima, lougit. totius -j vix 

 sequante ; auricula) valde inajquales, radiatim tenuiter costulata3, 

 postica minima, antica valvte dextroe interne profunde siniiata ; 

 costne valvae siuistrae interstitiis angustiores, valvtc dQxtrj3 

 latiores. 



Lougit. 38 millim., alt. 46, diam. ]1. 



Ilah. Mauritius. 



This beautiful species is distinguished by the very sloping 

 dorsal margins, which converge at the apex at an angle of 

 75° ; the very unequal auricles ; the elevated ribs, those of the 

 left valve being narrower than 

 the interstices or the cost^ of 

 the other valve ; the style of 

 coloration, which, however, is 

 variable ; the tine radiating strife 

 and the microscopic reticulation 

 or shagreened epidermal coating, 

 which everywhere invests the sur- 

 face and which is easily rubbed off 

 during the process of cleaning. 

 The central ribs of the left valve 

 have about seven raised lines do WTi 

 each, separated by striai or sulci 

 of about equal width, and the 

 grooves between the costas are 

 ornamented with about the same 

 number of lines. The valves 



are whitish within, and, being thin, the blotching of the 

 exterior, especially that of the left valve, is more or less 

 distinctly visible. 



This species differs from P. tigris^ Lam,, which in some 



