62 BRITISH OOLITIC AND LIASIC BRACHIOPODA. 



Obs. Sowerby's figures of T. fimbria illustrate only one of the states in which we 

 find this species ; nor docs it appear to attain much larger dimensions than those given 

 above (fig. 6). In the young state, and sometimes up to a considerable period of growth, 

 the shell is quite smooth, without any plaits or ornaments, the margin line being straight 

 all round (fig. 11); but in some rare cases, even when young, the ornaments of its surface 

 are slightly perceptible (fig. 12); at a more advanced period the surface of the valves, 

 towards the edge, becomes irregularly undulated, much in the way of a frill, as stated by 

 Sowerby, but not extending to the hinge-margin, which is always smooth, and regularly 

 curved and rounded. Nothing can be more irregular than the manner in which these 

 ornaments are presented in different specimens, as may be perceived by the several illustra- 

 tions we have selected ; at times, the whole surface of the valves is regularly rounded to 

 near the edge (figs. 6, 12); at other times, the smooth part is partially separated from 

 the plaited portion by a marked line of growth and a difference in level (figs. 2, 10), 

 proving that there was a sudden stoppage in growth, which, on being resumed, the shell 

 from smooth became undulated, or differently plaited. Sometimes, before the stoppage 

 alluded to, the shell had already become frilled, but on continuing the growth at a different 

 level these ornaments became differently disposed, having no continuity with the ones 

 already formed, as in fig. 10. These undulating plaits are also very irregular in their form, 

 in some cases a few small plaits are succeeded by a large one widely separated, others 

 close together : sometimes taking rise at about half the length of the valve, and, after 

 proceeding to some distance, separated into two or more bifurcations irregularly disposed 

 (figs. 7, S). 



The bifurcated plaits do not always reach the front, one or more disappearing at a 

 short distance from their origin, while some smaller plaits, at times, also appear between 

 the larger ones, so as to produce in that part of the shell a kind of irregular zig-zag 

 aspect. 



Ter. fimbria is very abundant in certain beds of the Inferior Oolite in different parts of 

 Gloucestershire, near Cheltenham, Minchinhampton, &c, whence many fine series have 

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

 common in most collections. We have not yet observed this species in any of the Conti- 

 nental localities ; but it is probable future researches may lead to its discovery, since 

 T. plicata, a species closely allied to it, has been found in Trance by M. D'Orbigny. 



Fig. 7 is from the collection of Professor Buckman ; fig. 8 from that of Dr. Wright. 



60. Terebratula flabellum, Defrance. Plate XII, fig. 19 — 21. 



Terebkatula flabellum, Def. Die. des Sciences Nat., vol. liii, p. 160, 1828. 



— palmetta, Deslonffchamps. 1837. Soc. Linn, de Normandie. 



— flabellum, Morris and Dav. Annals and Mag. of Nat. Hist., 1847, 



p. 256, pi. xix, fig. 2. 



— palmetta, Bronn. 1849. Index Palseont, p. 1244. 



— flabellum, D'Orb. 1849. Prodrome, vol. i, p. 316. 



