REPORT ON THE LAMELLIBRANCHIATA. 109 



(iriter coiivexa. Margo dorsi auticus pai'iim oljliquus, subrectiliiiearis, vix excurvatus, 

 posticus brevior, valde declivis, prope umbones levissime concavus, dein convexiusculus. 

 Margo veutris late curvatus, postice subsinuatus. Dentes cardinales duo insequales in 

 utraque valva. Dentes laterales validi, elongati. Pallii .sinus angustus, profundus. 

 Ligamentum internum obliquum, angustum. 



This species is small, thin, semipellucid, white or pale yellow, glossy and finely 

 concentrically striated, the striae being close and regular, and some of the interstices 

 towards the posterior end slightly elevated and lamellar. It is somewhat convex, 

 considerably inequilateral, of an elongate oval form, rather acuminate or shortly rostrate 

 behind and sharply rounded in front. The posterior dorsal slope is very oblique, slightlv 

 concave immediately behind the small acute beaks and then faintly excurved. The 

 anterior margin is much longer, almost straight, or very faintly arcuate at first, and 

 finally curving into the ventral margin forins an acutely rounded end. The lower 

 outline is broadly curved and indistinctly sinuated towards the hinder extremity. The 

 hinge is composed of two cardinal teeth in each valve, whereof the posterior in the right 

 and the anterior in the left are lari^er than the others and rather triangular. The 

 laterals are well developed, and the pallial sinus is deep, reaching within a short 

 distance of the anterior muscular impression. 



Length 8 mm., height 5, diameter 2^. 

 , Habitat. — Station 185b, east of Cape York, North Australia", in 155 fathoms; coral 

 sand. 



Tellina ( ?) casta, Hanley. 



Tellina casta, Hanley, Proc. Zool. Soc. Lond., 1844, p. 63.'' 



Tellina casta, Hanley, Sowerby's Thesaurus, vol. i. p. 253, pi. Ivi. tig. 9. 



Tellina casta, Sowerby, Conch. Icon., vol. xvii. fig. 269. 



Tellina (Areopagia) casta, Ecimer, Monogr. Conch. -Call., eJ. 2, p. 95. 



Habitat. — Torres Strait, in 3 to 1 1 fathoms (Challenger) ; Singapore (Hanley). 



This species is described as inequivalve, and it is the left ^•alve whirli is a trifle more 

 convex than the right. The dorsal margins are correctly said to he " on either side 

 nearly straight, moderately and nearly equally sloping." From this description it will 

 be seen that Sowerby's figure is somewhat inaccurate, giving a too decided convexity to 

 the anterior slope. There are two diverging cardinal teeth in the right valve, the 

 posterior of which is much the larger and bifid, and the lateral grooves are strongly 

 marked on both sides. On the contrary, in the left valve the anterior is the larger of 

 the two, and likewise cleft. The ligament projects but verj- little, and a portion of it 

 forming an internal cartilage is situated in a narrow pit just behind the cardinal 

 teeth. 



