210 CEETACEOUS PELECYPODA 



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

 1. Carditjm [Tiiachycardium] incomptum, Sowerhy, PL XI, Figs. 3-7. 



1846. C. incomptum. Sow., apud Forben, Trans., Geol. Soc, London, vii, p. 115, pi. 15, fig. 16. 

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



Tracli. testa siih-quadrcniQiilari, injlata, alt lore qnam lonr/a, siih-cBquiluternli, 

 antice lente rotunda ta, dccHvltate postica abrupt a, applanata, ad i)iarr/mem siibrecta ; 

 siiperjicie costis 25-30 radiantibus, distantioribus, acutis, confertim spinulose luhcr- 

 cidatis ornata ; margme interno crasse denfato ; cardine dentibus laterulibus cardi- 

 nalibus approximatis, omninis crassissimis instructo. 



Height of shell : its length ... ... ... ... 1-18 



Thickness „ : „ ... ... ... ... 0-91. 



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

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

 typical Trachj/cardiioji. The valves are strongly inflated, anteriorly gradually, 

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

 Avith from 25-30 sharp prominent and sjDiuous ril)s, less spiny on the posterior 

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

 ribs. Old specimens (figs. 3 and 1) have usually the ribs not so distinctly tuber- 

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

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



Z it t el identifies this species with Card. Ottoi, Geinitz, (Denksch. Akad., 

 Wien., xxiv, pt. ii, p. 144), 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 Forbes only mentions, " costis sub-squamosis." 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 Garudamuugalum and Serda- 

 mungalum, in a broAvnish calcareous rock, evidently formed of the detritus t)f 

 coral reefs ; common. 



Formation. — Trichinopoly group. 



2. Cakdium [Tkachycaedium] exulans, Stoliczka, PI. XI, Figs. 11-13. 



Track, testa parva, imdto ultiore quam longa, sub-ceqtiilaterali, antice lente 

 rotuudata postice late sub-trimcata, umbonibus angustis, prominulis, incurvis in- 

 structa, ab umbonibus ad marginem infero-posteriorem obtuse angulata, in superjirie 

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

 separutis ornata; margine interno dentato ; lunula hand diatincta ; cardine den- 

 tibus lateralibus cardinalibus valde approximatis instructo. 



Height of shell : its length ... ... ... ... I'^l 



Thickness „ : „ ... ... ... ... 1-09 



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

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



