from the Inferior Oolite of the Cotteswolds. 257 



Trigonia tuberculosa, Lycctt. PI. IX. fig. 9. 

 Trigonia tuberculosa, Lycett in Ann. & Mag. Nat. Hist. 1850, p. 422. 



Shell small, depressed, ovately trigonal; umbones recurved, 

 anterior and inferior borders rounded, posterior border slightly 

 excavated ; area small, transversely striated, the striatums being 

 large and irregular ; marginal and inner carina? narrow, elevated 

 and striated ; the tuberculated costae are numerous (18 in the 

 adult), curved concentrically with very densely arranged tuber- 

 cles ; the tubercles are rather depressed, ovate or clavate, their 

 longer diameter directed downwards. 



A pretty little species distinguished from the young of T. 

 striata by the more numerous costae and by the peculiarities of 

 the tubercles. 



It is rare ; for the present example I am indebted to the 

 kindness of the Rev. P. B. Brodie, who has procured several spe- 

 cimens in the shelly freestone of Leckhampton Hill. 



Trigonia clavo-costata, Lycett. PI. IX. fig. 6. 



Trigonia clavo-costata, Lycett in Ann. & Mag. Nat. Hist. 1850, 

 p. 425. 



Shell subtrigonal ; umbones obtuse, not recurved, anterior side 

 produced, its border rounded, posterior border straight, oblique 

 and truncated ; area flattened, finely striated transversely and 

 tricarinated ; the marginal and median carina? have regular mo- 

 derate-sized tubercles, the inner carina has numerous transverse 

 plications ; the other portion of the surface is ornamented with a 

 few rows of concentric tubercles ; the tubercles are large, about 

 eight in a row, the first two or three, and the latter one or two 

 rows consisting of costae which are not divided into tubercles. 



Compared with Trigonia decorata, it is smaller and shorter pos- 

 teriorly, the area has finer striations, the carina? have larger and 

 more distantly arranged tubercles, the concentric costae have 

 much larger tubercles ; they are about half as numerous as in 

 T. decorata ; lastly, the few primal costae are smooth, in the other 

 species they are tuberculated. 



A specimen in the cabinet of the author, and a second in that 

 of Dr. Wright, are the only examples with which I am acquainted ; 

 they are nearly of equal dimensions, and agree in all their cha- 

 racteristic features. 



Length upon the marginal carina If inch, opposite measure- 

 ment li inch. 



The building-stone of the Inferior Oolite which forms the 

 upper portion of its middle division is the seat of this species, 

 which has been obtained in the vicinity of Nailsworth. 



