TEREBRATULA. 61 



Diagnosis. Shell inequivalved, elongated, oval, tapering posteriorly ; valves convex, 

 sometimes gibbous; beak small, not much recurved, truncated by a circular entire foramen, 

 deltidium small, receding ; lateral ridges indistinct. Surface of valves smooth, up to a 

 certain age slightly undulating, or plaited towards the margin at a more advanced period. 

 Structure punctuated, loop short. Length 33, width 22, depth 17 lines. 



Obs. The term plicata has been given by Lamarck, Borson, and Say, to different shells 

 placed by them in the genus Terebratula, but which belonging to different genera are 

 only synonyms of other species ; therefore, we think Mr. Buckman's name, though of a 

 later date, may be retained, and that of Lamarck preserved for his species, which will have 

 to be placed in Fischer's genus Rhynchonella. M. D'Orbigny proposes to change 

 Mr. Buckman's name to that of Subplicatella, which I would have readily adopted, but for 

 the reason above given. Ter. plicata is quite smooth up to a considerable age, when the 

 frontal and lateral edges become more or less undulated or plaited; they never extend very 

 high up on the valves, but are restricted to near the edge, forming an irregular frill round 

 the shell, as seen in figs. 1 and 2. The plaiting in this species is very similar to that of 

 Ter. fimbria; but both species seem distinct. T. fimbria is much smaller, rounder, and has 

 not got that tapering of the posterior portion, so peculiar to T. plicata, which is likewise a 

 much larger shell. 



Ter. plicata is found along with T. fimbria in some of the beds in the Inferior Oolite, 

 in the neighbourhood of Cheltenham, Minchinhampton, &c, where many fine species have 

 been obtained by Dr. Wright and Messrs. Lycett, Buckman, Walton, Morris, and others ; 

 the three largest specimens with which we are acquainted may be seen in the collection of 

 the Geological Society and in those of Messrs. Morris and Buckman. 



It has also been found at Tournus (Saone et Loire), in France, by M. D'Orbigny. 



Fig. 1 is from a specimen in the Collection of the Geol. Soc. ; fig. 2 from the 

 collection of Professor Buckman ; fig. 5 from that of Dr. Wright. 



59. Tkrebratula fimbria, Sowerby. Plate XII, figs. 6 — 12. 



Terebratula fimbria, Sow. 1823. Min. Con., vol. iv, p. 27, tab. 326. 



— — Morris. Catalogue, 1843, p. 133. 



— — Bronn. 1849. Index Palaeont., vol. ii, p. 1236. 



— — UOrb. Prodrome, vol. i, p. 287, 1849. 



Diagnosis. Shell inequivalved, orbicular ; beak short, slightly recurved, and truncated 

 by a circular foramen, almost touching the umbo, and generally concealing the deltidium ; 

 lateral ridges indistinct, valves almost equally convex, sometimes gibbous, smooth in the 

 young state, irregularly undulato-plaited at a more advanced age towards the margin ; 

 structure punctuated. Loop simply attached to crura, and extending to less than half the 

 length of the shell. Length 20, breadth 18, depth 13 lines. 



