230 Mr. J. Lycett on some neiv species o/Trigonia 



as have been before figured and described are given as concisely 

 as possible. 



COSTAT^. 



Trigonia costata, Lam. Var. 1. costata. Var. 2. multicosta. 

 .\ar. S. pulla. Vav. 4. sculpta. 

 T. costatula, Lye. 

 T. exigua, Lye. 

 T. tenuicosta, Lye. 

 T. hemispharicay Lye. 



Clavellat^. 

 T. striata, Sow. 

 T. duplicata, Sow. 

 7". angulata, Sow. 

 T. signata, Ag. 

 T. tuberculosa, Lye. 

 T. v,-costata, Lye. 

 T. clavo-costata, Lye. 

 r. Phillijjsi, Mor. & Lye. I'ft/ . 

 Z". suhglobosa, Mor. & Lye. 

 J", gemmuta, Lye. 

 7\ decor at a, Lyo. 



Trigonia tenuicosta, Lycett, n. sp. PI. XL fig. d-a. 



Shell subhemispherical, moderately large, the anterior and 

 inferior boi'ders rounded, the posterior border slightly concave ; 

 umbones pointed, prominent and recm-ved ; 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 carinse, 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 carinas are very finely reticulated, 

 the lanceolate space between the inner carinse 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 carinte ; the costse 

 are much more numerous, and are scarcely separated from the 



