TEREBRATULA. 49 



Terebratula trilineata., Young and Bird. 1828. Geol. of York., pi. viii, fig. 17. 



— ovoides, Young and Bird. 1828. Geology of Yorkshire, pi. viii, fig. 12. 



— — Desk. 1836. Nouv. ed. de Lamarck, vol. vii, p. 361. 



— — Morris. 1843. Catalogue, p. 135. 

 lata, Morris. 1843. Catalogue, p. 134. 



— TETtiNEATA, Morris. 1843. Catalogue, p. 137. 



— ovoides, Bronn. 1849. Index Palaeont., p. 1244. 



— trilineata, Bronn. 1841). Index Falseont., p. 1 254. 



Diagnosis. Shell ovate, elongated, valves moderately convex, beak prominent, sub- 

 carinated and truncated by a rather large entire foramen, without distinct lateral ridges, 

 deltidium well defined, in two pieces ; lateral margin of valves straight with rounded front; 

 surface smooth, punctuated, and marked by concentric lines of growth. Length 2 inches 

 2 lines; breadth 1 inch 10 lines; depth 11 lines. 



05s. This species seems little known and has given rise to much confusion, but 

 having obtained the loan of a great many specimens, referred to it from Messrs. Sowerby, 

 Bowerbank, Ripley, C. B. Rose, Bean, Morris, &c, and from different localities, I was 

 soon convinced that Sowerby's Ter. ovoides was the same as his Ter. lata, which can be 

 perceived by the simple examination of PI. 100, of the ' Min. Con.,' which is only a 

 wider and more depressed specimen of the same species, nor does Sowerby's figures give 

 a very correct illustration ; it is also evident from a numerous suit of Young and Bird's 

 Ter. trilineata kindly sent me by Mr. Ripley, of Whitby ; this species must be also placed 

 among the synonyms of T. ovoides. These authors appear to have been only acquainted 

 with internal casts of these shells, since they state that the smaller valve is always marked 

 by three slender depressed lines diverging from the umbo, owing to which circumstance 

 they gave it the name of trilineata; these said lines are due to the central septum and 

 muscular impressions, visible on the surface of internal casts of most species of Terebratula, 

 and therefore cannot be used as a character ; they also allude to the difference observable 

 in width and length, as well as thickness, in this species ; it is the case too in Ter. ovoides 

 and lata of Sowerby, the pinched beak visible in many specimens, and especially in internal 

 casts, appears to be one of its characters. 



In PI. VITI, fig. 5, we have represented Sowerby's Ter. ovoides; fig. 4, his Ter. lata; 

 and figs. 6 — 9, Young and Bird's Ter. trilineata, which, as I stated, belong all to one type; 

 and as Ter. ovoides, Sow. appears the most common form, I have selected it to represent the 

 species, which is variable in its shape and dimensions; it is a flatfish shell, rarely very convex 

 or gibbose. M. Deshayes, in 1836, adopted the name of T. ovoides, and places lata among 

 its synonyms. Its Geological range has not yet been quite satisfactorily established ; 

 probably it lived during different deposits of the Oolitic series. Erom the Inferior Oolite 

 of Robin Hood's Bay, near Whitby upwards, Sowerby states his Ter. lata and Ovoides 

 occur in blocks, and sandstone containing green-sand, in alluvial deposits of gravel, frag- 

 ments of chalk, &c, in some parts of Suffolk. It is not, however, a Cretaceous, but 

 an Oolitic shell, as Mr. C. B. Rose admits, and in which opinion I entirely concur. 



