2G2 CRETACEOUS PELECYPODA 



List of cretaceous species. 



Pictet and Campiche, Pul. Suisse., 4™'' ser., 3™ part., p. 29G, only record the roll()wiii<j 

 two species under the name Biplodonta : — 



]--i. — My^ia Urgonensis, P. and C, and M. gurgiiis, P. and R. ; the first is from the Urij;'<iiiiiii, 

 the second from Gault-ljeds. 



In the list of the species of Lucina, I have particularly noticed the following as externally 

 resembling Ilj/sue : — L. globiformis, Leym., L.? sol'uhda, and X. Turonemis; the hinge-teeth of 

 these species should be carefully examined. 



3-5. — Mpia g'Mosd, Gabb, (Jour. A. N. Sc, pi. iv, p. 302), 1\I. parUis, Con., (ibid. p. 278), 

 and ? M. polila, Gabb, (Pal. Calif., i, p. 178,) are noticed from North America. 



6. — Hippagiis Aemilianus is the only species which represents this family in the South Indian 

 cretaceous rocks. 



I may also notice that Cyprimeria olesa, which d'Orbigny described as a Lncina (vide p. 180), 

 has the external form and the hinge-teeth somewhat resembling those of a Psatkura, but in the 

 I inly right valve which I have seen the anterior bifid cardinal tooth is much more oblique than in 

 Deshayes' typical Psalhura. However, better preserved specimens of both valves would deserve 

 a careful comparison regarding this point. 



HIPPAGUS, Lea, 1833, (see p. 260). 



1. HiPPAGTJS ^MiLiANUS, Stoliczkci, PI. XIV, Eig. 6. 



H. testa verticaliter ovali, mitlto altiore quam longa, valde injlata, nmhonihiis 

 ohtusiuscnlis, 2^romimilis, inciirvis, ap2^'>"oximatis instructa, crassiuscnla, sub-vitrea, in 

 sitperficie striis minutissimis svb-kunellosis concentricis ac alteris siib-obsoletis 

 7'adiantibus ornata ; regions lunulari et areali hand circimiscriptis ; canline edentulo 

 obsolete insimiato ; margine interna continuo, levi. 



Height of shell : its length ,., ... ... 1"44 



Thickness (of both valves) : „ ... ... ... 1'26 



I have already noticed tliat this species most closely resembles the eocene 

 IT. isocardioides, Lea, the type of the genus, which is only a little higher and 

 apparently somewhat shorter than our fossil. The shell itself is of considerable 

 thickness, and of a silky appearance, as commonly seen in recent species of Ilysia ; 

 the surface is covered with numerous striae of growth, some of which are stronger 

 than others, and towards the margin are intersected by deeper fuiTows ; besides 

 that there are numerous tine short interrupted radiating strise perceptible. 



Locality. — Stripermatur in whitish soft sandstone, in which a few specimens 

 only were discovered by the lamented Ch. Jilmilius Oldham, late Deputy Superin- 

 tendent of the Madras party of the Geological Siu'vey of India. 



Fonnation. — Arrialoor groujj. 



