170 Records of the Indian Museum. [Vor,. XIX, 



We remarked on the resemblance of the hinge of this form 

 to that of L. jenkinsianus. This resemblance is, however, super- 

 ficial only, for the pseudocardinal teeth in rhadinaeus are much 

 thinner and broader than in L. jenkinsianus and the laterals are 

 not so well developed. The shape of the shell also is different 

 resembling more the true L. niarginalis than any of the forms of 

 L. jenkinsianus. 



Photographs of typical specimens of different forms of the 

 latter are given on pi. IX, and of the hinge-teeth of the three forms 

 in text- fig. 2. 



Lamellidens jenkinsianus (Benson) subsp. obesa (Hanley 

 and Theobald). 



(PI. IX, figs. I, 2.) 



icSyy. Uiiio marginalis var. obesa, Hanley and Theobald, op. cit, p. 

 20, pi. xliii, fig. 3. 



I describe this subspecies before the t3q3ical form of the spe- 

 cies since the shell is of a more central type and this treatment of 

 the species makes it easier to understand the relationships of the 

 different forms. 



The shell in this species is elongate, subelliptical, posteriorly 

 produced into a spatulate process about the middle line of the 

 shell ; rather thick, convex and greatly inflated ; beaks rather 

 small but swollen, incurved and meeting in the middle line above, 

 with low somewhat curved corrugations in the 3^oung but eroded 

 in full-grown specimens ; surface marked with low concentric ridges 

 corresponding to the regions of growth. Dorsal slope nearly 

 straight in young but truncated anteriorly in adults, ventral mar- 

 gin straight or only slightly sinuate in its anterior part, curving 

 up in a regular slope posteriorly to form the lower border of the 

 spatulate process; anterior margin broad, regularly curved; post- 

 erior margin narrow, rounded ; posterior ridge straight or slightly 

 curved and with a narrow post-dorsal wing. Epidermis yellowish 

 to dark brown in the young, .becoming dark brown or even black some- 

 times intersparsed with yellowish-brown concentric bars in the adult. 

 Right valve with two lamellar pseudocardinals, of which the lower 

 is well developed, strong and rugose, in some specimens more so 

 than in others, and a single lamellar lateral, which is rather long, 

 originates from just below the beak and is only slightly arched. 

 Left valve with a well developed pseudocardinal, thick and more 

 ragged than those of the right valve and lying in front of the 

 beak, another pad-like tooth originating from underneath the 

 beak itself is also present ; and two blade-like slightly arched late- 

 rals of which the upper does not extend to the beak. Muscle-scars 

 shallow, but more impressed than in L. marginalis] anterior ones 

 separate, posterior confluent. lyigament very long and strongly 

 developed. Nacre bluish tinged with salmon, in young specimens 

 showing a purple band along the edge, iridescent. 



