176 CEETACEOUS PELECYPODA 



shells. In well presei-ved specimens the concentric ribs are thinner as compared 

 with the interspaces in which extremely fine concentric lines are traceable. AVhen, 

 however, the ridges of the ribs are a little worn off and thus become broader, 

 the interspaces have apparently the same width as the ribs. 



i:o(?aZ«7y.— Comarapolliam, in a light grey sandstone, apparently rare; only 

 three specimens were as yet found ; all are figured. 



Formation. — An-ialoor group. 



11. Cytherea [Callista] vagrans, StoUczka, PI. VII, Figs. 21-23. 



Cyth. testa late ovata, sen rotimdate quadrangulari, moderate convexmscida, con- 

 centrice liris subtillbiis numerosissimis siilcis angustis j^crum profiindis separatis 

 notata ; decUoitate limulare fere recta, areale convexiuscula ; lumda magna, ovata 

 linea impressa marginata, medio elevata ; area minima impressa ; margins antico, 

 ventrale ac postico uniforme-, ultimo qiiandoqiiam levissime- arcuato ; simi pallii 

 angusto, ohtusiuscido, ascendente. Cardo in valva sinistra dentihus tribus cardinali- 

 Ints et lino margine lunulari parallelo instriictus ; dentibus cardinaUbus diiobits 

 posticis in valva dextra ceteris mtdto crassioribus. 



Length of largest specimen ... ... ... ... 14 m. m. 



Height : length ... ... ... ... 075 



Thickness : height ... ... ... ... 0'66 



Shell ovate or sub-quadrangular, small, moderately convex, with very numer- 

 ous, close concentric not much elevated ribs ; beaks prominent, pointed, and 

 incurved ; lunular declivity almost straight, with the lunula ovate, proportionately 

 large, margined by a distinct groove and elevated along the central line ; posterior 

 declivity convex, the area very short, narrow and impressed, with the fulcra hardly 

 distinguishable ; anterior and posterior ends rounded, the former slightly produced ; 

 ventral margin more convex in the oval than in the sub-quacbangular forms ; 

 pallial sinus short, narrow, obtuse at the end and ascending. In the left valve 

 the cardinal teeth are thin, except the anterior, which is a little thicker than the 

 rest ; the lunular tooth is elongated and parallel to the margin. In the rio-lit 

 valve (a specimen from Comarapolliam) the two posterior cardinals are remarkably 

 thick, leaving narrow interspaces between them for the thinner teeth of the left 

 valve. 



Localities. — Comarapolliam and north-east of Kai'apaudy, in whitish conglo- 

 meratic sandstone (one specimen from each) ; Garudamungalum in bluish calcareous 

 sandstone ( two specimens ) ; south of Garudamvmgalum in brownish sandstone 

 (one specimen). 



Formation. — Arrialoor and Trichinopoly groups. The Comarapolliam specimen 

 is somewhat roundly sub-quadrangular, and has the two posterior cardinals, as 

 noticed above, remarkably thick, but there is no other difference in the ornament- 

 ation and structure of the shell. The specimen from Karapaudy is in every respect 

 identical with those from Garudamungalum, and is the largest. 



