10 BRITISH TERTIARY BRACHIOPODA. 



Ter. lunifera and seminuhm of Philippi 1 have been referred by some authors to this 

 genus, but I have been able to convince myself, from a perfect specimen of the last-named 

 species, that its internal arrangements are completely dissimilar to those seen in the 

 smaller valve of Argiope. 



The genus Argiope seems to have originated, as far as our present knowledge goes, 

 in the cretaceous period, and has continued to our day, one of the species, A. cistellula, 

 from the crag being likewise found recent. 



4. Argiope cistellula, 8. Wood. Plate I, fig. 13 8 4 . 



Terebkatula cistellula, S. Wood. 1840. Catal. of Crag Shells, Ann. and Mag. of 



Nat. Hist., vol. v, p. 253. 

 Megathiris cistellula, Forbes and Hartley. History of British Mollusca, pi. lvii, 



fig. 9, 1849. 



Diagnosis. Shell inequivalved, variable in shape, wider than long or otherwise, in 

 contour hemispherical or transversely suborbicular, more or less truncated above. Larger 

 valve more convex than the smaller one, in which a longitudinal, central depression is 

 visible, beginning at a short distance from the umbo, and extending to the front. Beak 

 produced, with depressed triangular area ; foramen very large, chiefly formed out of the 

 beak and area of larger valve, and completed by the hinge margin of smaller valve ; no 

 visible deltideal plates, a small groove only extending from the beak, along the edge of the 

 foramen. Hinge line straight, the central retrusion of the opposite margin shallow, but 

 distinct. The teeth and condyles on either valve are widely separated, owing to the dimen- 

 sions of the foramen. In the interior of smaller valve, a central septum proceeds from under 

 the crura, becoming gradually more elevated as it approaches the front, where it forms an 

 elevated cenfral, longitudinal plate, dividing the valve, on either side of which are seen 

 two slightly curved lateral elevations, not projecting much above the surface. In larger 

 valve, a slightly elevated longitudinal ridge is visible, extending from under the beak to 

 within a third of the length of the valve ; the interior and exterior of valves are strongly 

 punctuated ; often having the appearance of raised tubercles, the inner edge being 

 more or less thickened and radiatingly scabrous. Surface smooth, with only a few 

 concentric lines of growth. The colour is of a light, tawny yellow. Length 1, width 1, 

 depth a little more than half a line. Recent and Fossil. 



05s. The first discovery of this curious little Brachiopod is due to Mr. S. Wood, who 

 mentioned it under the name of Ter. cistellula, in his ' Catalogue of the Crag Mollusca,' 

 published in 1840, several specimens of which he had found in the Coralline Crag of 

 Sutton. Professor Forbes gives a good description of this shell, as found in the recent 

 state, in his valuable work on 'British Mollusca.' We there find stated, that a few 

 specimens had been found in forty fathoms of water by Mr. Jeffreys and Mr. Barlee, while 



1 ' Enutneratio Moluscorum Sicilise,' pi. vi, figs. 15, 16, 1836. 



