216 CEETACEOUS PELECYPODA 



CAHDIUM, Linne 1758, (see p. 207). 

 1. Caedium [Tkaghycakdium] incomptum, Sowerhy, PI. XT, Eigs. 3-7. 



1846. C. incomptum, Sow., apnd Forbes, Trans., Geol. Soc, London, vii, p. 145, pi. 15, fig. 16. 

 1850. idem, apud d'Orbigny, Prodrome, ii, p. 242. 



TracJi, testa sub-qtiadrangulari, inflata, altiore quam longa^ suh-cequilaterali, 

 antice lente rottmdata, declivitate postica abrupta, applanata, ad marginem subrecta ; 

 superficie costis 25-30 radiantibus, distantioribus, acutis, confertim spinulose tuber- 

 milatis ornata ; margine interno crasse dentato ; cardine dentibus lateralibus cardi- 

 nalibus approximatis, omninis crassissimis instructo. 



Height of shell : its length ... ... ... .,, i-ig 



Thickness „ ; „ ... ... ... , ... 0'94 



The shell of this species is sub-quadrangular in shape, like Acanthocardium, 

 but the hinge-line is short and the lateral teeth very close to the cardinal, as in 

 typical Trachycardium. The valves are strongly inflated, anteriorly gradually, 

 posteriorly somewhat abruptly, sloping and truncated. The surface is ornamented 

 with from 25-30 sharp prominent and spinous ribs, less spiny on the posterior 

 declivity ; the furrows are equally broad or, near the periphery, broader than the 

 ribs. Old specimens (figs. 3 and 4) have usually the ribs not so distinctly tuber- 

 culated as young ones, and sometimes they must have been greatly rolled before 

 being buried in the rock (see fig. 5). 



Zittel identifies this species with Card, Otto% Geinitz, (Denkseh. Akad., 

 Wien., xxiv, pt. ii, p. 144d), but the reason does not seem apparent, for the figure 

 given by Eorbes scarcely admits of any identification with a known species, and in 

 the description Eorbes only mentions, " (?os^i5 5^/5-5g^^6^mo5^5." I have compared 

 both the original specimens ; they are in a bad state of preservation, but clearly 

 belong to the present species. 



Localities, — Neighbourhood of Anapaudy^ near Garudamungalum and Serda- 

 mungalum, in a brownish calcareous rock, evidently formed of the detritus of 

 coral reefs ; common. 



Formation, — Trichinopoly group. 



\{ 2. Oardium [Teachycahdium] exulans, Stoliczha, PI. XI, Eigs. 11-13. 



Trach, testa parva, multo altiore quam longa^ sub-cequilaterali, antice lente 

 rotwidata postice late sub-truncata^ umbonibus angustis, prominulis, inciirvis in- 

 structa^ ab umbonibus ad marginem infero-posteriorem obtuse ang^data^ in superficie 

 costis 35-40 radiantibus, cequalibus obsolete granulosis, obtusis, sulcis angustissimis 

 separatis ornata; margine interno dentato; lunula haud distincta ; cardine den- 

 tibus lateralibus cardinalibus valde approximatis instructo. 



Height of shell : its length ... ... ... ... 1*41 



Thickness „ : „ ... ... ... ... 1-09 



This species is readily distinguished by its remarkable great height as compared 

 with its length, and by the obtuse ridge running from the apex to the infero- 



