﻿CLAVELLAT^. 29 



the number, character of, and description of the rows of costse ; with a single exception, 

 also, the condition of preservation assumed by these Kelloway Rock Trigonias is very 

 indifferent, and renders the task of description difficult and deficient in definition. 



The description of T. Rupellensis in the ' Prodrome ' of D'Orbigny is very brief, but 

 appears to be sufficient to characterize the species. It was also briefly alluded to, and its 

 more prominent features indicated, by Mr. Leckenby, in his ' Memoir on the Kelloway 

 Rock of the Yorkshire Coast.' It has occurred very rarely ; the original of our figure, from 

 Mr. Leckenby 's cabinet, is the only perfect example with which I am acquainted. 



Geological position and locality. The Kelloway Rock of Red Cliff, near Scarborough, 

 associated with T. paucicosta and numerous other fossils characteristic of that formation. 



The French specimens are from the Coral Rag of La Rochelle and Nantua. 



TaiGONiA siGNATA, J(^. Plate II, figs. 1, 2, 3. 



Tbigonia clavellata, Ziettien. Petref. Wiirtemburg, 1830, pi. Iviii, fig. 3. 



— SIGNATA, Agassiz. Trigonees, 1840, pi. iii, fig. 8 ; pi. ix, fig. 5 ; p. 18. 



— — B'Orbigny. Prodrome, 1850, tome i, p. 278. 



— DECORATA, Lyc. Ann. & Mag. Nat. Hist., 1850, vol. xii, pi. xi, fig. 1. 



— — Morris and Lyc. Gr. Ool. Monog. Pal. Soc, 1853, pi. xv, fig. 1. 



— — Morris. Catal., 1854, p. 228. 



— CLAVO-COSTATA, Lyc. Ann. Nat. Hist., 1850, pi. xi, fig. 6 (variety;. 



— SIGNATA, Oppel. Juraformation, 1856, p. 408. 



— CLAVELLATA, Quenstedt. Der Jura, 1856, pi. Ix, fig. 13. 



— SIGNATA, Dewalque and Chapuis. Pal. Luxemb., 1857, p. 172, pl.xxvi, fig. 1. 



Shell ovately elongated, sub-trigonal, depressed; umbones antero-mesial, small, and 

 not prominent nor recurved, but rarely they are more erect and recurved ; the anterior side 

 is moderately produced and rounded ; both this and the lengthened lower border are curved 

 elliptically ; superior border straight and lengthened, or, more rarely, somewhat concave ; 

 area wide, flattened ; its posterior extremity is compressed and somewhat truncated, 

 bounded by two delicate, minutely tuberculated carinsc, and traversed longitudinally by a 

 mesial furrow, and sometimes by a minutely tuberculated carina for about the half of its 

 length ; it is also transversely plicated, either coarsely or delicately ; in the former case the 

 tubercles of the inner carina forms varices or continuations of the transverse plications ; 

 the whole surface of the area measured transversely is upon the same plane. 



The escutcheon is depressed, lengthened, and narrow; its superior border is somewhat 

 raised. 



The costated portion of the shell has a numerous series (about twenty) of oblique rows 

 of tuberculated costse, of which the first-formed four or five are slightly curved, but are 

 nearly horizontal, delicate, and sub-tuberculated ; the rows which succeed are also raised ; 



