﻿CRETACEOUS BRACHIOPODA. 



27 



such as figs. 10 and 11, bear a certain resemblance to young individuals of Sowerby's 

 species. It shows also a great deal of variability in the degree of incurvature of its beak. 

 The nearest allied species seems to be the Terebratula Beaumonti, D'Archiac ; but this, 

 Mr. Meyer observes, has the beak much shorter and more abruptly truncated, while the 

 smaller valve is more inflated near the hinge-line. Internal casts show that the medial 

 septum in the dorsal valve extended to fully half the length of the valve. 



Position and Locality. This shell was first found by Mr. Meyer in the pebble-bed at 

 Tewsley, and at other places around Godalming. It is also extremely abundant in the 

 Upper Neocomian or Lower Greensand phosphatic beds at Upware, near Cambridge. 

 M. de Loriol informs me that he and M. Pictet have found specimens entirely agreeing 

 with those from Upware in the Upper Neocomian (Aptian) at St. Croix, in Switzerland. 



19. Terebratella Davidsoni, Walker. Sup., PI. VIII, figs. 1 to 7. 



Waldheimia? (Terebratella?) Davidsoni, Walter. Geol. Mag., vol. iv, p. 454, 



pi. xix, fig. 4, Oct., 1807, 

 and vol. v, p. 405, 1868. 



Spec. Char. Shell somewhat pentagonal or ovate, longer than wide, broadest about 

 the middle, tapering to the beak, truncated in front. Dorsal valve moderately convex, 

 most so at the umbo, flattened along the middle, slightly depressed near the front. 

 Ventral valve much deeper and more convex than the opposite one, subcarinate and 

 moderately arched in profile, laterally flattened ; beak rather long, slightly incurved and 

 truncated by a foramen which is more or less widely separated from the hinge-line by a 

 deltidium in two pieces ; .beak-ridges sharply defined. Surface of both valves ornamented 

 by numerous fine, radiating, raised ribs, which increase rapidly in number, after leaving 

 the beaks, by the interpolation of shorter ribs between the longer ones. The ribs are 

 also crossed at close intervals by numerous equidistant, more or less overlapping scale- 

 like ridges, as well as by concentric lines of growth. Loop elongated and doubly 

 attached. 



Length 16, width 11, depth 6 lines. 

 Obs. This fine species seems to be nearest allied to T. oblonga. Its loop much 

 resembles that of T. Fittoni in its arrangements. About forty-six ribs may, on an 

 average, be counted round the margin of each valve. It varies a good deal, some 

 specimens being much shorter, broader, and more convex than others, the deltidium 

 differing also a good deal in its dimensions. Internal casts show that the septum in the 

 dorsal valve extends to nearly half the length of the valve. Mr. Walker at first described 

 this species as a Waldheimia, but soon after discovered that it was a Terebratella. The 

 loop is attached as in Terebratella, but with a slight difference, for the extremity of the 

 reflected portion almost touches the septum. 



