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



This very delicate little species is readily separable from any of the species previously 

 described in this Keport by the fine and rather remote concentric lirse. It belongs to 

 Section M of the genus (see p. 38), characterised by a toothless hinge, concentric sculpture, 

 and a small posteriorly inclined ligament. 



Callocardia (f) pacifica, n. sp. {ride p. 156). 



A second specimen of this species, from the same locality, has fortunately been 

 preserved, having exactly the form of that previously described. The hinge in the right 

 valve is quite of the same character as that of Callocardia adamsii, consisting of a long 

 irregular tooth beneath and posterior to the beak, and a much shorter erect tooth in 

 front, separated from the posterior by a smaU notch, or, in other words, the hinge might 

 be said to consist of one elongate irregular tooth subdivided towards the anterior end by 

 a small notch. 



Leda prolata, n. sp. 



Testa parva, sequilateralis, antice acute rotundata, postice breviter rostrata, nitida, 



albida, incrementi striis sculpta. Margo dorsi utrinque subrectilinearis, leviter 



obliquus, ventralis curvatus, postice ad rostrum baud profunde sinuatus. Umbones 

 ad apicem obtusi, paulo prominentes. 



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



Habitat.— Station 256, July 21, 1875; lat. 30° 22' N., long. 154° 56' W.; depth, 

 2950 fathoms ; bottom, red clay ; Mid North Pacific Ocean, north of 

 the Sandwich Islands. 



This species very closely resembles Leda rectidorsata of Seguenza, 

 Leda prolata, n-sp. ^^^ "^^s dredged in deeper water than any other Lamellibranch 

 obtained during the Expedition. There being but a single specimen, 

 I have not ventured to open the valves in order to examine the hinge. 



Yoldia lioylei, n. sp. 



Testa parva, tenuis, ovata, insequilateralis, nitida, albida vel dilutissime olivacea, 

 striis incrementi tenuissimis sculpta. Umbones parvi, parum pro- 

 minentes, paulo excentrici. Linea cardinis gracibs, dentibus erectis sex 

 utrinque instructa. 



Toldia hoyki, n. sp. 



This species, judging from the two specimens at hand, is small, ovate, 

 highly glossy, a little inequilateral, and sculptured with very fine lines of growth. The 

 valves are very thin, almost equally rounded at the ends, but the curve on the longer 



