•220 THE VOYAGE OF H.M.S. CHALLENGER. 



Tliis species is flat, rhomboidal, very ine(|uilateral, white or pale l)rownisli and faintly 

 blotched with brown, concentrically finely costate, the ril:)s Ijeing sublamellar, 

 moderately remote, and roundly angulated at a faint raised indistinct ridge radiating 

 fx'om the beaks to the lower hinder extremity. The lunule is elongate, very narrow, 

 grooved on each side of a raised centre, and smooth. The posterior dorsal margin is almost 

 horizontal, straight, and longer than the anterior, which descends almost at right angles, 

 and is also rectilinear. The lower outline is very slightly excurved, and forms a rounded 

 corner at both ends. The dorsal area is linear, flat, and not aff"ected 1)y the concentric 

 ribs. The umbones are minute, acute, and peculiarly produced at the apex into a small 

 conical peak, and siti;ated a very little posterior to the anterior extremity. The two 

 i-ardinal teeth of the left valve are slightly divergent from one another, elongate and 

 slender, the anterior being a trifle the thicker, and about equal to the single tooth of the 

 other valve. The lateral teeth and srrooves are distinct and elongate. The outer surface 

 is everywhere very minutely sculptured with fine concentric striae which are broken up 

 1)V others that radiate from the umbones, a kind of sculpturing such as obtains in the 

 genus Myodora. The anterior muscular impression is elongate and subpyriform, the 

 posterior being rather larger and rounder. The interior is minutely denticulate along 

 the ventral margin, but smooth elsewhere. 



Length 8 mm., height 6, diameter 2^. 



Habitat. — Station 188, south of New Guinea, in 28 fathoms; also Station 187, near 

 Cape York, North Australia, in G fathoms. 



This is a pretty little species resembling externally the genus Myodora both as 

 regai'ds form and sculpture, but having the dentition and non-sinuatcd pallial line of 

 CrassateUa. This, togetlier with Crassatella aurora, belong to what 1 think is an 

 unnecessary subgenus [Crassatina) proposed by WeinkaufF, which is distinguished from 

 the typical Crassatella only by having the inner edge of the valves crenulated. 



Crassatella parva (C. B. Adams). 



Gduklia parva, C. B. Adams, Proc. Best. Soc. Nat. Hist., 184.5, p. 9. 



Astarte Imiulata, Conrad, Amer. Journ. Sci. and Art.«, 18tG, vol. ii. p. 393. 



Crassatella guadaloupensis, d'Orbigny, in Sagra's Hist. Cuba, vol. ii. p. 289, pi xxvii. 



figs. 24-26. 

 Gouldia giuidaloupensis, H. and A. Adams, Genera Moll., vol. ii. p. 485. 

 Astarte madracea, Linsley, Amer. Journ. Sci. and Arts, vol. xlviii. p. 27.5 (woodcut). 

 Gouldia mactracea, Gould, Invert. Ma.ss., ed. 2, 1870, p. 128, tig. 442. 

 Astaiie pifeifferi, Pbilijipi, Zeitscbr. Malakozool, 1848, vol v. p. 133. 

 Goiddia pfeifferi, Tryon, Proc. Acad. Nat. Sci. Pbilad., 1872, p. 249. 



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

 ooze. 



