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



Nucula (Acila) niirahilis, A. Adams and Eeeve. 



Nueula mirahilis, A. Adams and Keove, Zool. Voy. " Samarang," p. 75, pi. xxi. fig. 8. 

 NiiniJa mirahilis, Hanley, in Sowerby's Tbes. Coneli., vol. iii. p. l.^r), pi. coxxis. fig. 114. 

 NiLcula mirahilis, Dunker, ludex Moll. Japon., p. 238. 

 Nucula {Acila) mirahilis, H. and A. Adams, Gen. Moll., ii. p. 545. 



Habitat. — Station 233a, off Kobe, Japan, in 8 to 50 fathoms (Challenger) ; Kieu- 

 sieu, Nagasaki Bay (Adams ;ind Ree\'e). 



The single shell from Kobe is exceptionally large, being 30 mm. long and 21 iu 

 height. 



Nucutina, d'Orbiguy. 



Nuculina oralis (S. Wood) (PI. XIX. figs. l-\h). 



Pleu.radon ovalis, S. Wood, Ann. and Mag. Nat. Hist., 1840, vol. iv. p. 230, pi. xiii. fig. 1. 

 NiicineUa miliaris, (Deshayes?) S. Wood, Monog. Crag Moll., vol. ii. p. 73, pi. x. figs. 4, a-c. 



Testa parva, insequilateralis, altior quam longa, irregulariter oblique ovata, solidiuscula, 

 alba, Isevis, striis incrementi sculpta. Margo dorsi infra uraboues subhorizontalis, brevis, 

 parum arcuatus. Latus anticum paulo supra medium angulatum, supra angulum obliquum, 

 rectiusculum vel incurvatum, infra id leviter curvatum ; postieum latissime areuatum ; 

 inferius paulo excurvatum. Cardo validus, dentibus primariis 7-8 insequalibus, in 

 valva sinistra, lateralique elongato postico lamelliformi iustructus. Pagina interna baud 

 margaritacea, subnitida, cicatrice postica maxima notata, margine simplice, baud crenulato 

 •circumdata. 



This little species is much higher than long, somewhat obliquely and irregularly 

 ovate, moderately strong, not particularly convex, white, smooth, and sculptured with 

 fine lines of growth. It is a trifle inequilateral, the umbones being located just a little 

 behind the centre. The front side margin is at the upper part oblique, and almost 

 straight, or even very faintly incurved, then rather suddenly angulated, the angle falling 

 a little above the middle, beneath which it exhibits a faint curve. The posterior side 

 forms one regular very gentle arcuation, and the basal outline is only a little more 

 rounded. The hinge-plate is broad and in the left valve armed with seven or eight 

 primary teeth, of wliich two anterior and three posterior are somewhat stronger than 

 those intervening. They are prominent, pointed, separated by deep pits, and arranged 

 in a slightly curved series. The lateral tooth on the posterior side is long and thin, and 

 separated from the outer margin by a deep groove. The interior of the valves does not 

 appear to be highly glossy or pearly, is smooth at the margin, and slightly thickened just 

 within. The posterior muscular impression is remarkably large and situated low down 

 beyond the lateral tooth. 



Length 2^ mm., height 3^, probable diameter If. 



