63 



A flat, solid, obliquely oval shell; the auricles small, obtuse; 

 with 23 rounded smooth, thick ribs ; general colour, pale 

 straw, pale pink near the umbones, variegated with interrupted 

 angular bands of brightish red. We have only seen one 

 specimen of this magnificent shell which is in the collection 

 of Mr, Cuming. 



53. P. histrionicus. (pi. xx. f. 240.) Gmel. p. 3326. No. 54. 



T. oblique sub-ovali, compressa, sub-eequivalvi ; valva 

 dextra magis ventricosa, auriculis striatis, posticis minoribus, 

 anticisadbasin emarginatis ; costis valvse sinistra 15,rotundatis, 

 lateribus serratis, tribus lateralibus ; valvee dextrte duodecim, 

 centralibus hevibus, lateralibus serratis ; colore albo, valvee 

 sinistrse costis alternis nigro, alternis rubro, maculatis. Long. 

 1. lat. 0. 18.; alt, 0. 21.; poll. 



A flat shell rather spread out at the sides, and slightly elon- 

 gated at the posterior ventral margin ; the lower valve is slightlv 

 ventricose, and the upper valve flat ; the 7 central ribs are 

 broad, rounded, smooth on the top, and serrated at the edges ; 

 the 3 lateral ribs on each side are much narrower, and serrated 

 across, those of the under valve being 12 in number, and the 

 lateral ones only serrated: ground colour nearly white; some 

 of the ribs of the upper valve spotted with red, the inter- 

 mediate ones with black. Ceylon and Singapore. 



54, P. Radula. (pi. xvii. f. 154, 155.) Lin. Syst. Nat. 

 p. 1145. Ostrea maculosa? Gmel. 



T. sub-trigona, crassa, compressa, scabra, radiatim sulcata, 

 ad marginem postiee sub-elongata, ad latera sub-quadrata 

 auriculis sub-Eequalibus, obtusis, ad basin emarginatis, rugosis, 

 sulcatis, costis novem ad duodecim, elevatis, sub-quadratis, 

 crassis, sulcatis, concentrice lyratim striatis ; interstitiis latis, 

 sulcatis ; cardine oblique plicato ; colore pallide luteo, nigro 

 fuscoque maculato, vel fusco late fasciato et maculato. Long. 

 3. 40. ; lat. 0. 80. ; alt. 3. 80. ; poll. 



Rather trigonal, thick, rough, nearly equilateral, the posterior 

 margin slightly produced, and the sides flattened, the auricles 

 nearly equal, roughly ribbed ; the ribs vary in number 

 from nine to twelve, they are thick, elevated, rather square, 

 radiately grooved, and concentrically striated ; the interstices 

 are of the same shape, inverted ; hinge obliquely plicated ; the 

 ground colour is pale yellowish, spotted with brown or black, 

 sometimes nearly covered with broad brown bands. 



Ceylon. 



55. P. velutinus. (pi. xiii. f. 31.) nob. 



T. sub-ovali, sub-compressa, eequilaterali, radiatim leviter 

 striata, ad marginem sub inflata; auriculis sub-eequalibus, 



