78 CRETACEOUS PELECYPODA 



CEROMYA, Agassiz, 1842 (see p. 66). 

 V 1. Ceromya subsinuata, Forbes, sp., PL IV, Eig. 4. 



1846. Isocardia suhsinuata, Forbes, Trans., Geol. Soc, Lond., vii, p. 146, pi. 17, fig. 12. 



C. testa inflata, altiori quam tonga-, tenui, concentrice sutcato-striata, rotundata, 

 (squwatvi ; umhonibus productis, attenuatis^ distantibiis, antice versus vatde incmms, 

 sutca duptici haud profunda ab umbonibus usque ad marginem postero-inferiorem 

 decurrente instructa ; tunuta profunda, cordifonni, marginata ; cardine edentiilo, 

 duobus sutcis obliquis brevibus inter umbones sitis predito. 



Height of shell : its length ... ... ... ... 1'16 



Thickness „ : „ ... ... ... ... 1-04 



The external form of this species is perfectly similar to that of a Gtossus (Iso- 

 cardia), but it is readily distinguished from this genus by its thin shell and edentulous 

 hinge, the hinge-margin being simply a little indented at the termination of two short 

 grooves which run obliquely from the beaks posteriorly. Besides these there are two 

 other shallow grooves, which commence at the beaks and run along the posterior 

 margin of the shell to the infero-posterior end; the beaks are very prominent, 

 attenuated, and strongly incurved towards the front side ; the surface is regularly 

 concentrically striated and salcated. 



Locatity. — Pondicherry, in bluish calcareous sandstone ; rare. 



Formation, — Valudayur group. 



ANATINA, Lamh., 1809 (see p. 68). 

 1. Anatina (Cercomya) aucuata, Forbes, PL III, Eig. 1. 



1846. Anatina arcuata, Forbes, Trans., Geol. Soc, London, vii, p. 143, pi. 16, fig. 5. 



An. fCerc.) testa etongata, compressa, sub-cequilaterati ; parte antica paulo 

 altiori, ad marginem sub-rotundata ; umbonibus postice versus incurvatis, anguste 

 fissuratis ; parte posteriori angustata, rostriformi, prope marginem superiorem obtuse 

 bicarinata ; superficie costis concentricis distantibus, antice elegantim arcuatis ac 

 striis incrementi nmnerosissimis ornata, area postero-superiori solum minute striata. 



Height of shell at the beaks 

 „ „ anteriorly 



Thickness 



its length ... ... ... 0-24 



... 0-35 

 ... 0-14 



The two rounded keels along the upper margin of the posterior side include 

 an area which is merely striated, while the rest of the surface is covered with dis- 

 tant ribs and fine striae, and this character of ornamentation distinguishes the present 

 form from any other described from cretaceous deposits. The ribs are anteriorly 

 broadly and somewhat angularly rounded, and in this respect the species again mostly 

 resembles the Jurassic An. f Cere. J spatulata, Ag. The beaks are distinctly curved 

 towards the posterior end, close together, and narrowly fissured. 



Locality. — Pondicherry, in a pale bluish calcareous sandstone ; rare. 



Formation. — Valudayur group. 



