222 SUPPLEMENT TO THE BRITISH 



any Rhynchonella are cited in the works of foreign palaeontologists as having been 

 found in rocks of that period. The Rev. F. Sraithe has proposed for the species under 

 description the name of Glevensis, from Glevum, the ancient name of Gloucester. 



231. Rhynchonella capitulata, Tate. Dav., Sup., PL XXVII, figs. 11, 12. 



Rhtnchonella capitulata, Tate. The Yorkshire Lias, p. 424, pi. xv, fig. 24, 18"6. 



" Shell ovato-triangular, slightly transverse, with an elevated angular mesial fold ; 

 anterior third of the shell plaited, two to four (usually three) plaits on the mesial fold, 

 and about five on each lateral area ; the umbones gibbous ; from the appearance which the 

 gibbosity presents the shell has been named Capitulata. Beak thick, small, suberect. 

 The shell never attains any considerable size." 



The dimensions of the largest specimens are — breadth ^ inch, height -^ inch, 

 thickness -^ inch. 



Geological positions. — Middle Lias (Zone of Am. spinatus), main seam, where it is 

 very abundant, Eston, Challoner, Upleatham, and Hob Hill mines, Yorkshire (Tate). 



232. Rhynchonella spinosa, Schloth. Dav., Ool. Mon., p. 71, PI. XV, figs. 15 — 20. 



Rhynchonella spinosa is very variable in shape, and in the number of its spinulous 

 ribs, but I cannot agree with M. Koechlin-Schlumberger's statement (in vol. xiv, 2nd ser., 

 p. 166, of the 'Bulletin of the Geological Society of France' for 1856), that this shell 

 and Rh. senticosa should be considered one and the same species ; but I entirely concur 

 with him when he observes that he is against the system of restricting a species to a 

 certain bed or horizon, and giving it a new name should it be subsequently discovered 

 in a higher or lower horizon. But, at the same time, the error must be carefully 

 avoided of supposing that when allied forms occur on the same horizon they must 

 therefore be only varieties of the same species. Rh. spinosa occurs in great profusion in 

 the Inferior Oolite at Bradford Abbas, Crewkerne Station, and several other places both 

 in Dorset and Somersetshire. It has also been found by Mr. J. F. Walker in the 

 Fullers' Earth of Powerstock, near Bridport. 



233. Var. Bradfdrdiensis, Walker MS. Sup., PI. XXVII, figs. 18, 19. 



This appears to be a small variety of Rh. spinosa, resembling the young of Rh. concinna. 



