﻿CRETACEOUS BRACHIOPODA. 



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shell ; thence it tapers to the beak, which is nearly straight, and is truncated by a 

 large circular foramen ; beak-ridges rounded ; deltidium wide, in one piece. At the front 

 margin there is a wide central fold, formed by a depression of the ventral and a corre- 

 sponding elevation of the dorsal valve. Loop short." Dimensions : — Length 3 inches 

 4 lines, width 2 inches 11 lines, depth 1 inch 7 lines. 



This variety occurs at Upware. A fine series of specimens may be seen in the 

 Woodwardian Museum, Cambridge. 



47. Var. cyrta, Walker. Sup., PL IV, figs. 6, 7. 



Walker, Geol. Mag., vol. v, p. 404, pi. xviii, fig. 1, 1868. 



" Shell convex, inflated, width and length nearly equal, becoming flatter towards the 

 frontal margin ; beak short, rounded, truncated by a large foramen. Beak-ridges ill- 

 defined ; deltidium in one piece, wide, but shallow. Ventral valve globose ; dorsal valve 

 very globose towards the beak. Frontal margin not plicated ; the valves slightly flexuous. 

 Shell-surface smooth, marked with concentric lines of growth, and sometimes with 

 obscure radiating lines. Loop short." Dimensions: — Length 1 inch 11 lines, width 

 1 inch, 9 lines, depth 1 inch. 



"This variety occurs at Upware and at Potton along with the typical form, from 

 which it differs by its greater convexity, by its beak being shorter and more rounded, and 

 by its deltidium being much shallower." 



48. Var. Cantabridgiensis, Walker. Sup., PI. IV, figs. 8 — 10 5. 



Walker, Geol. Mag., vol. vii, 1870, p. 561, figs. 3, 4, 5. 



" Shell moderately convex, surface smooth, marked by concentric lines of growth ; 

 beak slightly recurved, deltidium wide, in one piece ; front margin of the ventral valve 

 slightly elevated at the centre, then depressed, and again elevated ; dorsal valve has two 

 ridges, which rise from near the centre of the valve, and terminate at the front margin, 

 having between them a wide central depression. Loop short." 



Length 1 inch 7 lines, width 1 inch 5 lines, depth 11 lines. 



" This form varies considerably with regard to the thickening of the front margin ; 

 some specimens have the front margin thinner and more rounded than the specimen 

 figured, but retain the same form of plication, being reverse to the var. T. uniplicata, 

 which has the central elevation on the dorsal valve and the depression on the ventral 

 valve. T. Cantabridgiensis differs from T. Dutempleana in having the beak less recurved 

 and the front margin more rounded. This variety approaches T.prcelonga in the plications, 

 but differs from that species in its greater width, form of its beak, &c." 



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