6 Mr. T. Davidson on the Brachiopoda 
1. Terebratula sinuosa, Brocchi, sp. PI. I. figs. 1-7. 
Anomia sinuosa, Brocchi, Conchiologia Fossile, vol. ii. p. 468 (1814), and 
We Bruguiére, Encyclopédie Meéthodique, tab. 239. fig. 3a, b 
Sp. char. Shell ovate, longer than wide, greatest width towards 
the middle; valves almost equally deep, uniformly convex from 
the beaks to about the middle of the shell, after which the dorsal 
valye becomes more or less prominently biplicated, with a sinus 
separating the two rounded ribs. In the ventral valve, a more 
or less apparent median elevation is margined by depressions or 
grooves of greater or less depth, and which correspond with 
the median sinus and ribs of the opposite valve; lateral mar- 
ginal line forming a gentle and regular curve, which becomes 
more or less biplicated in front. Beak rounded, incurved, and 
truncated by a large circular foramen, which is partly margined 
by a concave deltidium ; beak-ridges distinct only in the conti- 
guity of the foramen. Surface smooth, marked only by con- 
centric lines of growth. In the interior of the dorsal valve there 
is a very short simple loop, not much exceeding a fourth of 
the length of the valve, and confined to the posterior portion of 
the shell: this loop is attached by its crura to the hinge-plate, 
the two riband-shaped lamellz being soon united by a transverse 
lamella bent upwards in the middle. Shell-structure punctured. 
Proportions very variable: a large specimen measured in length 
3 inches, width 2 inches 7 lines, depth 1$ inch. 
Obs. It is exceedingly difficult to specifically discriminate be- 
tween some of the many biplicated Terebratule which occur so 
abundantly in the Jurassic, Cretaceous, and Tertiary formations ; 
and I must admit that it would be impossible for me to find 
words wherewith to distinguish the shell under description from 
certain allied forms which occur in the above-named formations*, 
* T have seen and possess several examples of T. perovalis, T. inter- 
media, T. biplicata, Sow., &e., which, although im all probability specifi- 
cally distinct, agree very closely in external form with some examples of 
T. ampulla and T. sinuosa. Nor will it be out of place to remark that 
many specimens of T. sinuosa from Palazzo in Tuscany do exactly agree 
im size and shape with Brocchi’s description and figure of T. biplicata; 
and we should have felt disposed to consider them synonymous had not 
MM. Saemann, Triger, and E. EK. Deslongchamps assured us (in a paper 
read before the Geological Society of France on the 16th of December 
1861) that the original specimen upon which Brocchi had founded his 
T. biplicata was derived from the Jurassic period. I, however, quite con- 
cur with what M. KE. E. Deslongchamps subsequently stated, at p. 136 of 
his excellent monograph of the Jurassic Brachiopoda of France, viz. that 
the imperfect preservation of the beak of Brocchi’s original (?) example of 
T. biplicata, as well as the uncertainty connected with its origin, makes it 
desirable that the terms T. biplicata and T. indentata, as applied by 
Sowerby, should be retained, and that the nomenclature should not be 
