252 Mr. J. Lycett on some new species of Trigonia 



ClAVELLATjE. 



T. striata t Sow. 



T. duplicata, Sow. 



7". angulata, Sow. 



T. signata, Ag. 



T. tuberculosa , Lye. 



T. v,-costata, Lye. 



T. clavo-costata, Lye. 



T. Phillipsi, Mor. & Lye. var. 



T. subglobosa, Mor. & Lye. 



T. gemma ta, Lye. 



T. decorata, Lye. 



Trigonia tenuicosta, Lycett, n. sp. PI. IX. fig. 4 a. 



Shell subhemispherical, moderately large, the anterior and 

 inferior borders rounded, the posterior border slightly concave ; 

 umbones pointed, prominent and recurved ; costse very numerous, 

 not much elevated, closely arranged, gracefully curved and almost 

 united to the marginal carina ; area very large, its surface forms 

 a considerable angle with the costated surface of the shell ; it 

 has three carina?, the median and inner of which are small but 

 distinct, and finely striated throughout their length ; the mar- 

 ginal carina is delicate, striated, rather acute and very much 

 curved ; the spaces between the carina? are very finely reticulated, 

 the lanceolate space between the inner carina? is large and very 

 finely reticulated. 



The great convexity of the valves and incurved figure of the 

 umbones produces a considerable curvature in the marginal 

 carina, and the costated portion of the shell near to the umbones 

 is very narrow ; the length of the marginal carina is somewhat 

 greater than the diameter of the shell at right angles to it. From 

 Trigonia costata it is distinguished by the more acute recurved 

 apex, by the small and finely striated marginal carina, by the 

 delicate and finely striated median and inner carina? ; the costa? 

 are much more numerous, and are scarcely separated from the 

 marginal carina ; the entire form is smaller and unlike T. costata ; 

 the area is alike in both the valves. 



It is somewhat rare ; all the examples have been obtained in 

 the upper division of the Inferior Oolite. 



Professor Buckman has obtained it near Cheltenham ; my own 

 specimens are from the Gryphite grit of Rodborough Hill near 

 Stroud. 



Trigonia hemispharica, Lycett, n. s. PI. IX. fig. 2. 



Shell small, its length not exceeding 3 lines, veiy much arched, 

 so that the diameter through both the valves slightly exceeds the 



