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



truncated ; area moderately large, flattened, transversely ribbed, 

 and having an obscure oblique mesial furrow, no distinct carinae, 

 the marginal carina being replaced by a series of small nodulous 

 elevations upon the posterior extremities of the costae. Costae 

 smooth, curved, closely arranged, rounded, and slightly bent 

 upwards as they approach the area, their number being about 

 fourteen. 



The costae upon the area are smaller and rather more nume- 

 rous, for an intercalated rib is sometimes added. Specimens 

 vary from 2 to 5 lines in length, the latter dimensions seeming 

 to represent the adult form. 



From T. costatula it is distinguished by the much smaller 

 dimensions and by the absence of any distinct marginal carina, 

 the costae being continued over its position upon the area. 



Trigonia concinna, Rcemer, Nord. Ool. Nachtrag. p. 35. tab. 19. 

 fig. 21. approximates to our shell in the general figure and dis- 

 position of the costae, but his shell would appear to have greater 

 convexity and a larger area, and the costae upon the area appear 

 to be as large as those upon the other portion of the surface ; it 

 is therefore probably a distinct species. 



Our little shell occurs not uncommonly in the shelly freestone 

 of Leckhampton Hill ; it has also occurred in the same beds near 

 to Nailsworth. 



Trigonia v.-costata, Lycett. PI. IX. fig. 7. 

 Trigonia x.-costata, Lycett in Ann. & Mag. Nat. Hist. 1850, p. 422. 



Shell ovately trigonal, moderately convex, anterior and infe- 

 rior margins rounded, posterior margin straight or slightly con- 

 cave ; umbones obtuse, slightly recurved ; area narrow, flattened, 

 its upper portion transversely plicated, its lower portion nearly 

 smooth, divided in its middle by an obliquely longitudinal fur- 

 row ; marginal and inner carinae but faintly marked and striated, 

 the inner carina being crossed by several varices. The costae are 

 very numerous, smooth and regular, they are directed from the 

 anterior border obliquely downwards and backwards nearly 

 straight to the middle of the shell, and there form acute angles 

 with varices which proceed upwards nearly vertically to the mar- 

 ginal carina ; the varices are slightly nodulous, they are fewer 

 and larger than the anterior costae. The first eight or nine 

 costae form only curvatures, and are not broken into two por- 

 tions. 



The species which approaches most nearly to the present shell 

 is T. angulata, Sow., but the figure of the two is different ; the 

 latter shell is more elongated and rostrated, the posterior border 

 is much more concave, the umbones arc more recurved, and con- 



