﻿SCABRiE. 



129 



lower geological position than pertains to T. caudata. The name is intended as a 

 trifling recognition of valuable and cordial assistance and information rendered to the 

 author by Mr. Etheridge, F.R.S., and of the interest which he has uniformly taken in 

 the progress of this Monograph. 



Trigonia caudata, Ag. Plate XXVI, figs. 5, 6, 6 a, 6 b, 7. 



Trigonia caudata, Agassiz. Trigonies, p. 32, tab. vii, figs. 1 — 3, 11 — 13, 1840. 

 _ _ jyOrbigny. Pal. Fran., Terr. Cret., vol. iii, p. 133, pi. 187, 1843. 



— — Forbes. Quart. Journ. Geol. Soc, vol. i, p. 244, 1845. 



— — Marcou. Jura Salinois, p. 142, 1846. 



— — Fitton. Strata at Atherfield, Journ. Geol. Soc, vol iii, No. 11, 



p. 313, 1847. 



— — TfOrhigny. Prodrome de Paleont., vol. ii, p. 78, 1850. 



— — Buvignier. Statist, geol. mineral, et paleont. de la Meuse, p. 473, 



1853, 



— — Studer. Geol. du Schweiz, vol. ii, p. 281, 1853. 



— — Morris. Catal., p. 228, 1854. 



— — Cotteau. Moll. foss. de l'Yonne, p. 76, 1854. 



— — Pictet et Renevier. Pal. Suisse, p. 97, pi. xiii, figs. 1, 2, 1857. 



— — Raulin et Leymerie. Statist. l'Yonne, p. 424, 1858. 



— — Desor et Gressly. Etud. geol. sur le Haut Jura, p. 37, 1859. 



— — Be Loriol. Descr. des Anim. invert, du Haut Salins, p. 73, 1861. 



— — Coquand. Monogr. Etage Aptien d'Espagne, p. 133, 1866. 



Shell subcrescentic, much inflated anteally, compressed, attenuated and rostrated 

 posteally ; umbones large, elevated, sub-involute, and recurved, their apices are 

 attenuated and contiguous when the valves are closed ; the anterior side is short, forming 

 a wide and somewhat depressed surface, arcuately curved with the lower border, which is 

 irregularly dentated by the extremities of the costse ; it is somewhat excavated or sinuate 

 posteally. The ligamental space is narrow, lengthened, and inter-umbonal, extending 

 both anteally and posteally to the umbones. The escutcheon is large even when 

 compared with other lengthened examples of the Scabrcs, forming a deep concavity 

 occupying almost the whole of the upper surface of the shell ; its upper border is raised 

 and dentated by the extremities of a series of costellse, elevated, narrow, and wrinkled 

 or scabrous, passing obliquely across its surface ; immediately between the umbones the 

 transverse costellae pass across a groove, which forms the commencement of the area, and 

 are united to the costae on the other portion of the valve. The area commences as a 

 furrow, which in its course downwards becomes bounded by gradually widening rounded 

 elevations, traversed transversely by numerous lines or plications, which upon 

 approaching the widening posteal extremity become large, irregular, and rugose. The 



