1881.] THE SURVEY OF H. M.S. 'alert.' 43 



opposite side being well withia the outer edge, with a groove be- 

 tween it and the margin for the reception of the submiirginal tooth 

 of the other valve. External ligament small, yet distinct. Internal 

 cartilage mimite, placed immediately beneath the apex of the valves. 

 Pallial line simple. 



To this genus belong Cardita tegulata. Reeve, and C. semen. 

 Reeve, the former from Valparaiso, the latter from Bolivia. 



Carditella pallida, sp. n. (Plate V. figs. 9-9 b.) 



Shell triangularly ovate, equilateral, small, compressed, white, 

 clothed with a very thin pale-olive epidermis, with 14 or 15 flattish 

 radiating ribs about twice as broad as the sulci between them ; also 

 concentrically sulcated and striated. The fine sulci cut through the 

 eostse, and, being rather close together, produce upon them, toward 

 the ventral margin, transversely oblong granules. Higher up the 

 ribs become narrower, and consequently the granules are not so large 

 or so wide. Interior of valves dentate at the margin. Two lateral 

 teeth in each valve, one marginal, the other within the margin. 

 One cardinal tooth in right valve, and two in the left. Ligament small, 

 external. ^Iso a very minute internal cartilage, immediately below 

 the apex of the umbo. Muscular scars subcircular. Pallial line 

 indistinct, but apparently simple. Length 4^ millims., diam. a, 

 thickness 2.7. 



Hab. Stadon 2. 



Cardita Jlabellnm, Reeve, is almost precisely like this species 

 exteriorly ; but the lateral teeth in the former are much more delicate, 

 the internal ligament considerably larger, and the cardinal teeth are 

 not quite the same as in the specimens above described, consisting 

 of a single tooth bordering one side of the cartilage-pit and two 

 diverging ones united above on the other. In addition to these 

 differences, C.flabellum has no external ligament. For it I propose 

 the generic name of Carditopsis. C. tec/ulata. Reeve, is more in- 

 equilateral, less triangular, and has only twelve radiating ribs. 



Mytilus fischerianus, Tapparone-Canefri, Viaggio della Ma- 

 genta, p. 138, pi. iv. f. \-\b. 



Hab. Tom Bay, on a stranded mass of kelp. 



Care must be taken not to confound this species with the large 

 Chilian species M. chorus, Molina. It differs from it in form very 

 considerably. The greatest width in M. chorus is from the dorsal 

 angle to the opposite margin, which is remarkably straight. In 

 the present species, on the other hand, the greatest breadth occurs 

 considerably lower down, and the ventral border exhibits a regular 

 though slight curve. The muscular scars, too, offer excellent dif- 

 ferences. The anterior subumbonal is very indistinct and almost 

 apical in M. chorus, and that on the opposite or ligamental side is 

 rather remote from the umbo and of a broad ovate form ; whilst in 

 M. fischerianus the former is very distinct, deep, subtriangular, and 

 more remote from the apex, and the latter is quite narrow and 

 nearer the umbo. The large anterior scar of Molina's species is less 



