82 BRITISH OOLITIC AND LIASIC BRACHIOPODA. 



hinge margin of larger valve indenting that of smaller valve ; valves ornamented by 

 rounded costae, variable in number, proceeding from the beak and the umbo to the front 

 and sides, but faintly marked at their origin ; twelve or thirteen on each valve, four or five 

 of which in general form the mesial fold, to which a sinus and plaits in the other valve 

 correspond ; structure imperforated ; length 6, width 6, depth 4 lines. 



Obs. This shell is abundant in the Free Stone above the Pea Grit, in the Inferior 

 Oolite of Leckhampton Hill, near Cheltenham, where it was discovered by Dr. Wright ; 

 its plaits become distinct only towards the centre of the valves from which they proceed 

 to the front and sides ; B. oolitica, somewhat resembles certain varieties of B. variabilis, 

 or rather the variation triplicata of Phillips, found in the Lias near Radstock, but in the 

 last the beak is wider and more circular than in that of B. oolitica, which is generally 

 acute and tapering; the valves being likewise less convex and widest at their anterior 

 portion. 



Plate XIV, fig. 7. A specimen natural size, from the collection of Dr. Wright, 

 fig. 7 c d . The same enlarged. 



75. Rhynchonella Moorei, Lav. Plate XV, figs. 11 — 14. 



Diagnosis. Shell inequivalved, circular, nearly as wide as long; beak acute, not 

 much produced, more or less recurved ; foramen small, entirely surrounded by the 

 deltidial plates ; beak-ridges well defined ; hinge line not much indenting that of the 

 smaller valve ; valves convex, slightly depressed, and ornamented by a variable number 

 of radiating plaits, from eleven to eighteen on each valve, three, four, five, six, and even 

 seven forming a slightly produced mesial fold with corresponding plaits in a similarly 

 shallow sinus. Structure unpunctuated ; length 7, width 8, depth 5 lines. 



Obs. This little species was found by Mr. Moore in the Upper Lias, near Ilrainster, 

 and in the same beds at Tor Hill, Glastonbury. It seems to me quite distinct from 

 B. variabilis, being more circular, less convex, and ornamented in general by a much 

 greater number of plaits ; I have examined examples of all ages, from one line in length 

 up to seven, which seems to be the largest dimensions it attains. In such variable shells 

 as most Rhynchonellse, it is often very difficult to describe certain differences in the general 

 aspect, compared with those presented by other species closely approaching them, and 

 which appear to be distinct. 



The specimens figured are principally from Mr. Moore's collection. 



76. Rhynchonella Bouchardii, Dav. Plate XV, figs. 3 — 5. 



Diagnosis. Shell circular, semi-globose, as wide as long, valves almost equally convex ; 

 beak acute, moderately produced, rounded and more or less recurved ; foramen entirely 



