Bay of Bengal and the Arabian Sea. 13 
usual. ‘The hinge and the muscular impressions are precisely 
similar. Mr. Brazier has just recorded Oryptodon flexuosus, 
another British species, from New South Wales and Tas- 
mania, and it is gratifying to strengthen his statement by 
recording the occurrence of another species from our coasts in 
tropical seas. 
Cryptodon investigatoris. (Pl. IL. figs. 6, 6a.) 
Testa oblonga, subquadrata, valde inequilateralis, antice concave 
truncata, alba, equivalvis; valva dextra crassiuscula, concentrice 
tenuiter striata, antice profunde lunulata, carina mediocriter 
acuta ab umbone ad latus posticum decurrente instructa, inter 
carinam et marginem dorsalem valde excavata, infra carinam 
leviter depressa, carina secunda acuta, margini dorsi subparallela 
instructa ; umbo terminalis, antice curvatus, acutiusculus ; margo 
dorsi postice tenuis, acutus, parum arcuatus, versus umbonem pro 
ligamento anguste sulcatus, posticus superne sinuatus, in medio 
ad finem carine inferieris prominens, infra levissime sinuatus, 
deinde curvatus ; margo inferior rectiusculus, dorsali subparallelus, 
antice subincurvatus ; lunula profunda, carina obtusa marginata ; 
pagina interna antice et versus lineam pallii radiatim striata ; 
cicatrix posterior parva, sub extremitate marginis dorsalis sita, 
antica indistincta; linea pallii simplex; carine externe intus 
sulcis subprofundis indicate. 
Longit. 38 millim., alt. 27, diam. 26. 
Hab. Station 151, off Colombo, Ceylon, in 142-400 
fathoms, 
Only two right valves of this species were obtained ; but, 
judging from the even level of the margin and the position of 
the pallial line, there is little doubt but that this shell is 
equivalve. The deep groove from the umbo to the posterior 
end of the valve is much deeper than in the type of the 
genus, Cryptodon flexuosus, and the keel which limits it 
beneath is very acute, but not so acute as the carina which 
marks off the area between it and the dorsal line. 
Cryptodon philippinarum (Hanley). 
Lucina philippinarum, Hanley, Cat. Biv. Shells, p. 348, pl. xiv. fig. 18; 
Reeve, Conch. Icon. pl. iv. figs. 18 a, b. 
Lucina (Anodontia) philippinarum, Martens, Journ. Linn. Soc. Lond. 
1887, vol. xxi. p. 174. 
Austriella sordida, Tenison-Woods, Trans. R. Soc. Vict. 1881, vol. xvii. 
p. 83, pl. (unnumbered) figs. 10, 11. 
LInucina induta, Stoliczka, Martens, op. ett. p. 174. 
Hab. Philippines and Mergui (Hanley); Manila and 
