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



Jeflreys, wlio, with his accustomed eoui'tesy, kiudly examined tliis species, and showed 

 me tlie specimens of Arcafrielei figured in the Proc. Zool. Soc. Lond. 



Area (Scapharca ?) culebrensis, n. sp. (PL XVII. figs. 9-9?>). 



Testa transversa, valde inaequilateralis, antice angustata, postice dilatata, utrincpie 

 rotundata, alba, tenuissime cancellata, plus minusve granulata. Valvse tenues, semi- 

 pellucidse, impressione baud profunda ab umbonibus ad marginem ventralem paulo ante 

 medium leviter sinuatum signatse. Umbones parvi, parum prominentes, Isevigati, 

 subapproximati, circa in I longitudinis positi. Dentes circa 8, ntrinque divergentes, in 

 medio interrupts 



This sj)ecies is very inecj^uilateral, longer than high, much narrower in front than 

 behind, where it may l^e said to lie dilated. Both extremities are rounded, and tlie 

 ventral margin, which ascends oblicpiely towards the anterior end, is faintly incurved a 

 little in advance of the middle at the termination of a shallow depression, which extends 

 from the beaks downwards. The valves are thinnish, semitransparent, white, and 

 sculptured with numerous very fine radiating and concentric Lirse, the points of inter- 

 section being, as frecjuently is the case, somewhat thickened, and on the posterior side 

 distinctly granulose. The umbones are not much raised aliove the dorsal line, situated 

 from one-fourth to one-fifth of the total length from the anterior end, and smoothish 

 at the tips, which are only a little apart. The hinge-plate is consideral)ly shorter than 

 the valves, and is furnished with about eight divergent teeth, of which three are in front 

 of a central edentulous space and five behind it, the whole series forming a nearly straight 

 line. Owing to the transparency of the valves, more or less of the external ornamentation 

 is visible within. 



Length 5 mm., height 3^, diameter 2^. 



Habitat. — Station 24, ofi" Culebra Island, West Indies, in 390 fiithoms ; Pteropod ooze. 



This species is very like the variety septentrionalis of Area pectunculoides, Scacchi, 

 Ijut rather more oblique in growth, more sharply rounded behind, with the umbones 

 more anterior, &c. 



Area (Trisis) semitorta, Lamarck. 



Area semitorta, Lamarck, Anim. sans vert., ed. 2, vol. vi. p. 460. 

 Area semitorta, Eeeve, Concli. Icon., vol. ii. pi. xiii. fig. 89. 



Habitat.— Torres Strait, 3 to 12 fathoms (Challenger); Port Essington (Brit. Mus.); 

 Zebu, Philippines (Cuming); Tasmania (Lamarck). 



The last locality has not, I believe, been confirmed. 



