OP SOUTHEEN INDIA. 21^ 



posterior angle of the periphery ; the surface is ornamented by numerous (35-40) 

 closely set radiating ribs, which are only very slightly tuberculated ; in some 

 specimens they appear almost smooth. The short hinge-line characterizes this form 

 as a Tracliycardium. 



When the surface of the shell is worn off the ribs sometimes become bifid, 

 but their abnormal state is readily traced. 



io(?a?i^i^s.— South-east of Arrialoor and at Olapaudy; very common at the 

 former in a light coloured soft sandstone; the largest specimen measures about 

 40 m.m. in height. 



Formation, — Arrialoor group. 



\/ 3. Gaed. [Thachygaudiifm] productum, Sowerhj, PI. XI, Pigs. 15-16. 



1832. C. productum, Sow., Trans., Geol. Soc, London, iii, p. 417, pi. 39, fio-. 15. 



1865. idem apud Zittel, Denksch. Akad., Wien, xxiv, pt, 2, p. 140, pi. 5, fig. 4, cum synon. 



Trach, testa crassa, valde inflata, suh-quadrangulari, altiore quam longa^ 

 margine antico ac postico fere parallelism infero convexiusculo^ verticihus valde pro- 

 minentibus et incurvatis, Superficie costis radiantibus numerosis ad medium leviter 

 furcatis unilateraliter spinulose tubereulatis sulcis angustis disjunctis instructa; area 

 cardinali curvata, dentibus lateralibus ab cardinalibus moderate remotis^ omninis 

 crassis. 



Height of shell : its length ... ... ... ... 1-25 



Thickness „ : „ ... ... ... ... Q-gg 



This species is so well known that it is unnecessary to add anything to the 

 above description. The statement, however, that not the ribs but the intervenino* 

 sulci are spinulose or tuberculated rests, I believe, upon a mistake. The fact seems 

 to me that the tubercles or spines are situated only on one side of the ribs, reaching 

 down to the base of the adjoining furrow, and pointing either towards the anterior 

 or the posterior end. When the surface of the shell is somewhat eroded the 

 tubercles very easily wear off on the ribs, but they remain preserved in the adjoining 

 farrows, thus giving the impression that they were originally and solely situated in 

 them. A perfectly similar case can be observed on the recent Card. [^Tr achy car dium'] 

 elongatum, Sow. 



The species occurs from the Cenomanien up to the Senonien beds, almost 

 throughout Europe, in Germany, Belgium, Prance, and throughout the Alpine 

 Gosau deposits ; it is one of the cosmopolitan species, like FrotocaTdittm hillanum. 



Locality .--ILoiQimiQ, in a brownish calcareous sandstone; apparently rare. 



'Formation. — Ootatoor group. 



3 a 



