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



Mactrajacksonensis, n. sp. (PI. V. figs. 9-9&). 



Trigonella pusilla, Angas (non A. Adams), Proc. Zool. Soc. Lond., 1867, p. 916. 



Testa parva, paulo inaequilateralis, triangularis, albida, radiis paucis fuscis plus minusve 

 distinctis ornata, tenuis, nitida, striis concentricis tenuibus sculpta. Margo dorsi utrinque 

 valde declivis, vix arcuatus vel subrectus ; margo veutris late arcuatus, parum ascendens. 

 Cardo angustus, dentibus gracilibus munitus. Pallii sinus parvus, minime profundus. 



This species is of small size, triangular, considerably acuminate behind, and rather 

 more obtusely rounded in front. It is a little inequilateral, the posterior side being a trifle 

 longer than the anterior. It is thin, glossy, finely concentrically striated, the striae being 

 about as fine at the sides as on the centre of the valves. It is whitish, varied with about 

 six more or less distinct brownish rays. The dorsal margins are almost rectilinear, and 

 rather sloping, especially the posterior, which is a trifle longer than the anterior. The 

 umbones ate small, acute, white, and defined on each side by brownish rays. The interior 

 of the valves is very similar in colour to the exterior, and exhibits a very small delicate 

 hinge and a very shallow pallial sinus, extending only about one fourth of the length 

 across the valve. 



Length 14^ mm., height lOg, diameter 6. 



Habitat. — Port Jackson, Sydney, in 2 to 10 fathoms. 



This species must not be confounded with the young form of Mactra pusilla. It may 

 easily be distinguished by the following difl'erences. It is more acute behind and has 

 the posterior side longer than the anterior, whilst in Mactra pusilla the relative sizes are 

 reversed. The present species too has pale imibones, also lacks the conspicuous sulci on 

 each side upon the dorsal areas, and has a smaller pallial sinus. 



Family A n a T i n i d jj. 



Subfamily Pandorin^. 



Ca'lodon, Carpenter. 

 Coelodon elongatus. Carpenter. 



Caelodonelongatus, Carpenter, Proc. Zool. Soc. Lond., 1864, p. 600. 

 Coelodon elongatus, Carpenter, Moll. West. N. Amer., p. 229. 



Habitat. — Flinders Passage, North Australia, in 7 fathoms. 



The shells originally described by Carpenter were from China and Borneo. The 

 single specimen from the aljove locality difi'ers in one or two points which are not, I 

 consider, of specific importance. The hinder portion of the dorsal line is rather less 



