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



iiiirrower and longer than any of tlif other forms, oval, a little narrower posteriorly than 

 in front, and somewhat inequilateral, the hinder side being the longer. It is glossy, 

 sculptured with fine lines of growth, and furnished with about fifteen hinge-teeth 

 altogether (six anterior and nine posterior), which are peculiar in having their inner side 

 rise direct from the inner margin of the hinge-plate, and in being less obliquely placed 

 than usual, and rather far apart. 



Pectuneulus, Lamarck. 



Pectunculus pectinatus (Gmelin). 



Area pecfi /lata, Gmelin, Syst. Nat., p. 3313. 



Pectuneulus pedinatus, Lamarck, Anim. sans vert., ed. 2, vol. vi. p. 494. 



Pectuneulus pectinatus, Ileeve, Conch. Icon., vol. i. pi. vi. fig. 28. 



Habitat. —Station 113, off' Fernando Noronha, in 1010 fathoms; hard ground. 



The few specimens I have seen of this species all agree in having a small brown 

 blotcli on the dorsal margin on each side of the umbones, and a much more conspicuous 

 oblique ray on each side but more remote. This feature is best seen when the umbones 

 are towards the eye. 



Pectuneulus stellatus (Bruguiere). 



Area stellata, Brnguiere, Ency. Meth., p. 117. 



Pectuneulus stellatus, Lamarck, Anim. sans vert., ed. 2, vol. vi. p. 491. 



PeetHncnhis stellaius, Reeve, Conch. Icon., vol. i. pi. ii. fig. 5. 



Habitat. — Tenerife, in 70 fathoms (Challenger). 



The Tenerife .shells are mostly of a purple-reddish tint, zoned at intervals with a 

 darker colour, and invariably have the white star-shaped patch at the umbones. They 

 are also rayed with slender white lines, and some of the specimens ai'e ornamented with 

 wavy concentric reddish lines. The interior of the largest shells is generally totally 

 white, but some of the smaller specimens have the central portion of the valves stained 

 and blotted with deep purple -brown. 



The epidermis of this species is very deciduous, only the smallest portion at the 

 circumference of the valves apparently ever remaining. It is not of the hairy character 

 of Pectuneulus pilosus, Pect^inculus siculus, and some others, but has a more chaffy 

 appearance. The surface of the valves, besides the concentric lines of growth, has 

 scarcely any sculpture, the fine radiating striae met with in Pectmiculus siculus and 

 some others being entirely absent. 



