312 THE VOYAGE OF H.M.S. CHALLENGER. 



Habitat. — Station 185b, cast of Cape York, North Australia, in ].'35 fatlioms ; coral 

 sand. 



This species differs from Amussium caduciim not only in having more internal 

 costella3 but also in form and the sculpture of the exterior. 



Amussium scituhim, n. sp. (PI. XXIII. figs. 4-46). 



Testa (juveuis ?) parva, compressa, all)a, tenuis, subfequivalvis. Valva dextra 

 lineis incrementi paucis hie illic cisteris majoriljus instructa, sinistra liris numerosis 

 radiantibus, aliisque minus conspicuis concentricis concinne cancellata. Auriculae 

 mediocres, paululum ina^qnales, antica valvse dextrae prope marginem obliquum 

 dorsalem canaliculata, lirisque radiantibus paucis subgranulosis ornata, et antica et 

 postica in valva sinistra cancellatis. Pagina interna liris tenuibus circiter denis ad 

 marginem productis instructa. 



Of this species only a few valves were obtained, possibly representing but the 

 young form of it. It is a thin shell, semitransparent white, a trifle inequivalve, much 

 compressed, and about as long as high. The right valve is slightly deeper than the 

 left, and sculptured only with the concentric lines of growth, of which a few are more 

 raised than others. The left valve, in addition to the raised lines of growth, has a 

 considerable number of fine radiatiuo- lirse, Qjiviusr the surface a more or less cancellated 

 appearance. The beaks are acute, the converging dorsal lines meeting at an angle of 

 about 90 or 95 degrees. The ears are a little unequal, the anterior of the right valve 

 being somewhat channelled close to the oblique dorsal slope and ornamented with a few 

 radiating raised lines which are somewhat granular or subsquamous through being 

 crossed by other raised lines of growth. The posterior auricle in this valve, on the 

 contrary, is almost destitute of sculpture. Both ears in the left valve have radiating 

 and cross lirjE, the former predominating, and being, on the anterior auricle, prettily 

 scaled near the dorsal slope. The internal liraj are ten in number and produced to the 

 outer margin, where sometimes they are slightly thickened. 



Length 4i mm., height 4^, diameter 1^. 



Habitat.— Utatioii 188, south of New Guinea, in 28 fathoms; green mud. 



This sijecies differs from Amussium torresi in sculpture and the number of 

 internal ridges. 



Amussium squamigerum, n. sp. (PI. XXIII. figs. 5-5o). 



Testa ecjuilateralis, couvexiuscula, rotundata, alba, subpellucida. Valva dextra 

 concentrice laminata, iamellis teuuissimis numerosis supra porca? nonnullas radiantes 



