H I P P P U S . 



I'late I. 



Genus llll'POrUS, Memdiea. 



Testa aqiiivalvis, rcyularis, ince(ju'dateraHs, lunula, fere 

 clausd. Cardo deidibus duobas compresnis inaquuUbus 

 posticis inserti.s. Ligamentum margbmle, externum. 



Sliell equivalve, regular, inequilateral, with the lunule 

 almost closed. Hinge composed of two unequal, 

 compressed, posterior teetii, interlocking with one 

 another. Ligament marginal, external. 



The genus Hippopus, of which the well-known Cltama 

 Idppopus of Linnanis is still the only species known, dif- 

 fers from Triduciia, the nearest allied form, in having the 

 lunule, the anterior concave depression of the shell, nearly 

 closed. It will be readily iniderstood, therefore, that the 

 animal has very little, if any, byssus. It seems strange 

 that no second species of this well-detined generic type 

 should have been discovered, but such is the fact. Hip- 

 popiiH maculatus has been known for more than a century, 

 antl is collected and imported in great abundance from the 

 Eastern seas. 



Species 1. (Mus. Brit.) 



Hippopus maculatus. Hipp, testa subtrigouo-ovatd,tra- 

 peiiformi, aiifice late liinulatil, medio veutricosn, ver- 

 sus lutera constriclu, radialini costatd et liratd, pro- 

 fuse sqnaiuatd, squamis parvis,foliolatis, spinoso- imbri- 

 catis ; viariaureo-ulbd, purpareo-roseo vivide maculatd. 



The spotted Hippopus. Shell somewhat triangularly 

 ovate, trapeziform, anteriorly broadly lunulate, ven- 

 tricose in the middle, constricted towards the sides, 

 radiately ribbed and ridged, jirofusely scaled, scales 

 small, leaf-like, spinosely imbricated ; marble-white, 

 richly spotted with purple-rose. 



Clicima hippopus, Linnaius, Syst. Nat. p. 1137. 

 Hippopus maculatus, Lamarck. 



Hab. Eastern seas. 



This very elegant shell is too well known to need any 

 comment on its specific characters, which are in all re- 

 spects unique. No other species of the genus has been 

 collected, and there is no variation even of the sjiecies 

 worth calliuK attention to. 



June, 1S62. 



