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



fere obsoletis. Margo dorsi anticus rectiusculus, cleclivis, posticus paulo magis obliquus, 

 levissime excurvatus. Margo inferior antice inque medio arcuatus, propc extremitatem 

 posticam ad terminum impressionis late ab umbone radiantis conspicue sinuatus. Area 

 dorsi postica lata, porca rotundata marginata, prope medium porcam parvam mimi.s 

 conspicuam exhibens. Linea cardiuis crassa dentibus ad 20 elongatis acutis muuita. 



This small species is about equilateral, ovate-triangular, rounded in front and acutely 

 peaked behind. It is rather convex and solid, exhibits a shallow radiating depression 

 down the posterior side, is whitish, glossy, and sculptured with rather strong concentric 

 lirge which are attenuated and somewhat obsolete on both sides. The front dorsal margin 

 is straightish and moderately oblique, the posterior a trifle more sloping and very faintly 

 excurved, and the lower outline is gently convex in front and at the middle, but 

 conspicuously sinuated at the beaked end. The hinge-plate is strong, and armed with 

 about twenty long, sharp teeth, of which there are one or two more behind the cartilage- 

 pit than in front. 



Length A^ mm., height 3, supjjosed diameter of perfect shell 2^. 



Habitat. — Station 120, off Pernambuco, in 675 fathoms; red mud. 



I have ventured to describe this species from a single valve only, as its form is 

 peculiar, and the sculpture well marked. 



Leda jeffreysi, Hidalgo. 



Leda lata, Jeffreys, Ann. and Mag. Nat. Hist, 1876, vol. xviii. p. 431. 



Leda jeffreysi, Hidalgo, MolL Marin. Espana, p. 136; and Journ. de Conch., 1877, vol. xxv. 



p. 396. 

 Leda jeffreijm., Jeffreys, Proc. Zool. See. Lond., 1879, p. 579, pi. xlvi. fig. 2. 

 Leda Jeffreys!, DaU, Bull. Mus. Comp. Zool., vol. ix., No. 2, p. 124. 



Hahitat.—iitaiioTL 78, oS" the Azores, in 1000 fathoms ; and Station 344, off" Ascension 

 Island, in 420 fathoms. 



The specimens from the latter locality are more pointed anteriorly than those from 

 Station 78, approaching in outline Leda lenticula, MoUer, a nearly related species. 



Leda hebes, n. sp. (PL XIX. figs. 7-7a). 



Testa ovata, postice acuminata, antice acute rotundata, mediocriter convexa, inferuc 

 late curvata, nitida, alba, concentrice tenuiter striata. Margo dorsi anticus declivis, jDaulo 

 couvexus, posticus longior, subrectus, sequaliter obliquus. Lunula inconspicua, angusta, 

 marginata; area j^ostica latior, utrinque carinata, carina altera graciliori utrinque medium 

 instructa. Linea cardinis modice valida, dentibus circiter decem anterioribus, tredecimque 

 posticis instructa. 



