618 



20. Cyther^a planulata (pi. cxxvii. f. 13), Broderip, Zool. 

 Journ. vol. v. p. 48. Donax Lessoni ? Deshayes, Enc. Meth. vers. 

 p.99. C. planulata, \^x.stiffusa, Sowerby, Zool.Proc. 1835. p. 45. 



Cyth. testa trigona, depressiuscula, suboequilaterali ; angulis 

 inferioribus rotundatis ; pallidc Havicaute, radiis numerosis fusces- 

 centibus ; intus albida, f usco-violaceo varia ; dente postico remoto. 



Shell triangular, depressed, not quite equilateral (the hinder 

 side being the shorter), white, with a thin epidermis, radiated 

 with brown stripes of various width, purple at the apex and also 

 witliin at the sides and about the hinge ; near the hinder angle 

 there is a sinuous opening between the valves. 



The variety described in the Zoological Proceedings presents 

 a slight difference in form, and has the rays more spread. 



Panama. Cuming. 



21. Cyther^ea undulata (pi. cxxvii. f. 12), Bowerhy,jun. 

 C. planulata, Sowerhy, Beechy Voy. Zool. t. 43. f. 6. 



Cyth. testa C. planulata simih, sed altiore, solidiore ; radiis 

 interruptis, transverse undulatis ; latere postico clauso ; lunula 

 lanceolata, distincta. 



Shell less elongated, more equally triangular, and more soHd 

 than C. planulata, with the hinder side closed, or nearly so, and 

 painted with a defined broad ray of purplish-brown ; the rays on 

 the sui'face are composed of beautifully undulated cross bands ; 

 the lunule is long and distinct ; the purple patches within well 

 defined and brilliant. Umbones white. 



Salango, West Columbia ; sandy mud, nine fathoms. Cuming. 



22. Cyther^a polita (pi. cxxvii. f. 14), 8owerhy,jun. 

 Cyth. testa trigona, depressa, polita, postice angulata, pallide 



fulva, cinerascente, distanter radiatim fulvo fasciata, ad umbones 

 angulatim lineata, intiis alba; cardine, lateribus et margine 

 purpureo tinctis ; latere postico ad basin subacuto, latere antico 

 rotundato ; lunula parva, distincta, subinflata. 



A more smooth and solid shell than C. planulata or C. undulata ; 

 not squared, but angulated at the posterior termination of the 

 lower margin ; colour pale brown, with here and there a tint of 

 blue, and three or four brown rays ; umbones small, with very 

 delicate fluctuating lines ; inner surface white, tinted at the hinge, 

 the posterior side, and about the pallial impression with clouded 

 purple. 



Mr. Hanley has kindly furnished the only sjjecimen we have 

 seen of this shell. 



