TEREBRATULA. 47 



17. Terebratula ovata, Sowerby. Plate IV, figs. 6 — 13. 



Terebratula ovata, Sow. Min. Con., vol. i, p. 46, tab. xv, fig. iii, 1812. 



— — Parkinson. An Int. to the Study of Org. Remains, 1822. 



— — Fleming. A History of British An., vol. i, 1828. 



— — Woodward. Synop. Table of Br. Org. Rem., p. 21, 1830. 



— — Brown. 111. of Foss. Conch, of Gr. Br., pi. lv, figs. 34, 35, 1838. 



— — Morris. Catalogue of British Fossils, 1843. 



— Tennant. A Strat. List of British Fossils, p. 47, 1847. 



— lacrymosa, J)' Orb. Pal. Franc. ^Ter. Cret., vol. iv, p. 99, pi. 512, 



figs. 6 — 11, 1847; and Prodrome, vol. ii, p. 1/2, 1850. 



— carnea, Bronn. Index Pal., p. 1232, 1848. (Non T. carnea, Sow.) 



Diagnosis. Shell ovate, or oblong-ovate, depressed; beak produced, recurved, 

 obliquely truncated by a rather large circular foramen, partly formed out of the substance 

 of the beak, and completed by two small deltidial plates ; beak ridges well denned, leaving 

 a slightly concave false area between them and the hinge margin. Valves unequally convex, 

 the smaller or imperforated one is less so than the other ; uninterruptedly convex to the 

 margin in the young state, but soon assuming a longitudinal depression, appearing at 

 about the middle of the valve, extending and becoming deeper as it approaches the front. 

 In the larger valve, a corresponding longitudinal elevation or keel occurs ; marginal line 

 wavy, and in front indented by the smaller valve. Surface covered by irregular elongated 

 longitudinal elevated rugse, little interrupted in the middle of the valves, but on the 

 sides diverge and form innumerable small oblong tubercules, sometimes extending above 

 the surface of the shell in the form of short spines. Concentric lines of growth numerous ; 

 structure distinctly punctuated, interior unknown ; dimensions variable, the largest example 

 yet found measuring, length 19, width 13, depth 11 lines; but the greater number of 

 specimens do not attain these dimensions. 



Obs. This is one of Sowerby's first-described species, which he obtained at "Chute, 

 near Heytesbury, in Wiltshire." The species is perfectly known in England, and one of 

 the most abundant of the tribe found in the Upper Green Sand of the locality above named, 

 and discovered likewise by Messrs. Moore and Morris in the Chloritic Chalk of Chard and 

 Chardstock ; these specimens, however, rarely preserve the remarkable structure which cha- 

 racterises the species, from the nature of the sediment in which they were deposited having 

 deteriorated the surface of most of them; this character was not observed by Sowerby; 

 but, as the species is very common, it is not very difficult to procure specimens preserving 

 their structure; and some, in the collections of Messrs. Cunnington, Moore, and Morris, 

 show it to perfection. Many authors on the continent, among others Professor Bronn, 

 have erroneously believed it a synonym of Ter. Carnea, 1 that species not having been 



1 Dr. Mantel], in his 'Geol. of the South Downs,' p. 209, 1822, erroneously places T. ovata, Sow., in 

 the Upper and Lower Chalk, where the Sowerby type has never been as yet found. It is probable that this 

 error is the cause of foreign authors believing T. ovata, Sow., to be a synonym of Carnea. 



