SUPPLEMENT. 9 



this remarkable variety. It is rare. The matrix of these fossils is tough and hard, and 

 required a considerable expenditure of time, labour, and steel implements to bring these 

 specimens to their present condition. The two larger and more perfect specimens (PI. 

 II, figs 1, 3) were obtained at the cross-roads near Over Norton, the others (PI. IV, figs. 

 2, 4) in the lower beds of the Inferior Oolite at Rollright. 



Possibly the remarkable shell figured by Quenstedt, * Der Jura,' a Swabian species, 

 tab. 60, fig. 13, under the name clavellata, should really be arranged with this variety of 

 T. signata, of which it has the usual rugose aspect, more especially in the characters of 

 the costae, fewer in number, broken and irregular, with their cord-like tubercles extending 

 even to the pallial border ; the stratigraphical position appears also to agree with that of 

 this variety. The hard, unyielding matrix is altogether unlike the more sandy stratum 

 in the upper beds of the formation which have yielded the Zietenii variety ; it may be 

 compared rather with the Clypeus-grit of the Cotteswolds. 



Trigonia siGNATA, Af/.^ voT. Stutterdi, Lycett. Trigon. Supplement, Plate II, figs.^9, 



10, II; Plate IV, figs. I, 5, 6.*" 



The shell, less depressed than in the former two varieties, is more sub-ovate and 

 less lengthened ; the umbones are prominent, and are more recurved and less forward ; the 

 anterior side is more produced ; the hinge-border is shorter, and more distinctly concave ; 

 the area is wide and flattened, much expanded posteally ; on each side it is bounded by a 

 prominent row of large, rounded, regular carinal tubercles ; the median carina is repre- 

 sented by an obscure row of small tubercles ; the transverse plications are inconspicuous ; 

 near the apex they become linear, and are very closely arranged. The sides of the valves 

 have more convexity than in the former varieties ; the rows of costaj are much less 

 numerous, and more widely separated ; they are very regular in their arrangement, and 

 are all curved obliquely ; the few latter-formed costae are curved upwards nearly perpen- 

 dicularly, as is usual in the shells of T. signata ; the tubercles are larger than in the 

 other varieties, and less numerous, more especially in the latter-formed rows ; they are 

 moderately rounded, excepting near to the pallial border, where they become cord-like, 

 but are continued even to the border. The lines of growth are remarkably large and 

 conspicuous over the whole of the valves ; the first-formed two or three rows of costse are 

 plain, as in the other varieties. The number of tubercles in the rows are comparatively 

 few ; the largest are about the middle of each row ; they become attenuated as they curve 

 upwards in their approach to the marginal carina. 



The present variety presents an approach to the well-known T. clavellata ; a com- 

 parison of specimens show that the Inferior-Oolite Shell has the umbones more recurved, 

 the hinge-border shorter, and the rows of costse with a greater curvature. The pecu- 



