18 BRITISH FOSSIL TRIGONLE. 



It is from the Cornbrash of Marquise, and is named by him T. Bouchardi ; unfor- 

 tunately no figures o£ this and other new species incidentally and briefly mentioned in 

 that work have been given, and, in the absence of any allusion to the difference of the 

 costa3 near to the apex, I consider that the species in question is not sufficiently 

 characterised to constitute it an authority. 



Stratigraphical position and locality. The only example at our disposal was obtained 

 by Mr. Walton in the Great Oolite near to the Box Tunnel, Bath. 



§ II. ClAVELLATjE. 



Trigonia clavellata, Sow. Plate I, figs. 1, 2. 



CURVIROSTRA RUGOSA CLAVELLATA MAJOR, Luid. Litho., 1699, p. 36, pi. i.X, fig. "00. 



Trigonia clavellata, Sow. Min. Conch., 1815, pi. lxxxvii. 



Lyrodon clavellatum, Gold/. Petref., 1834 — 1840, p. 200, pi. cxxxvi, fig. 6, c, d, e, 



and f, excl. fig. 6 b. 

 Trigonia clavellata, Morris. Catal., 1854, p. 228. 



— ■ — ■ Damon. Geol. Weymouth, Suppl., 1860, pi. iv, fig. 2. 



(Exclude the figures of T. clavellata in the works of Parkinson, Young and Bird, Bronn, Zeithen, 

 Agassiz, Zwingen, Goldf., Petref., pi. cxxxvi, fig. 6, b ; also of Hebert, "Trigonees clavelle'es," Jour, de 

 Conchyl., 1861, pi. vii, fig. 1.) 



Shell ovately trigonal, moderately elongated, convex ; umbones large, obtuse and 

 incurved, but rarely recurved ; anterior side rounded, but not much produced, its lower 

 extremity curved with the lower border ; superior border straight, lengthened, sloping 

 obliquely downwards ; escutcheon flattened, its length is nearly equal to half the length 

 of the marginal carina ; the area is narrow, flattened or slightly convex, transversely 

 irregularly plicated, having three carinse, of which the mesial carina consists of a row of 

 delicate, regular, small tubercles ; the two bounding carinas have the tubercles much larger, 

 but depressed and closely arranged, those upon the inner carina form lengthened 

 transverse varices ; a well marked furrow borders upon the median carina, and in some 

 specimens the furrow is bounded upon each side by a row of tubercles ; more frequently, 

 however, the second or upper row is very imperfectly indicated ; the superior half of the 

 area is more depressed than the other portion. The sides of the valves have the rows of 

 tuberculated costse at first oblique, but the later-formed few become more horizontal 

 or more nearly accord with the direction of the lines of growth, so that the greater 

 number of the rows reach the anterior border in the form of small attenuated or sub- 



