34 BRITISH CARBONIFEROUS BRACHIOPODA. 



simple, or here and there bifurcated, or trifurcated near the margin. The sinus is of moderate 

 depth. The measurements taken from two examples have produced — 



Length 20, width 34, depth 14 lines. 

 12, „ 22 „ 11 lines. 



Obs. Few species seem to be more variable in shape and character than the one I am 

 now describing, and it was only after considerable hesitation — and the examination of a vast 

 number of specimens — that I could make up my mind to consider the extreme forms 

 delineated in PI. VII, figs. 7 — 1G, as belonging to a single species, viz., Sp. grandicostata, 

 and of which I have also reproduced the original illustration (PL V, figs. 38, 39). In the 

 single representation given by the author of ('British Palaeozoic Fossils') the lateral 

 margins are abruptly attenuated, as in some of the figures in my PI. VII, but this is not 

 the constant peculiarity of the larger number of individuals, in which the cardinal extremities 

 are not extended to the same extent as in the representation of the original type. It is 

 further observed by Professor M'Coy that " this shell is allied to Sp. trigonalis of Martin, 

 but differs from it by its abruptly narrowed and attenuated sides, and by its few very large 

 angular ribs occupying the body of the shell, and the abrupt diminution in size of the five 

 or six outer ridges on each side. A very young specimen, nine lines wide, has the three 

 ridges in the mesial hollow distinctly marked, but nearly as large as the lateral ones, of 

 which there are three or four great ones on each side, but scarcely a trace of any additional 

 ones on the flattened cardinal angles, which are strongly striated parallel to the angles." 

 I may here observe that, although I have observed the apparent diminution in width of 

 the five or six outer ribs alluded to, they are far from being so in the greater number of 

 specimens, in which the ribs gradually diminish in width and dimensions from either side of 

 the mesial fold, as in most other species of Spirifer. The proportion and dimensions of the 

 ribs on the mesial fold is also very dissimilar in different individuals, but in no case have 

 I observed them as large as upon the lateral portions of the valves. Professor De Koninck, 

 to whom I have forwarded a proof of my plates, thinks that perhaps the shells in question 

 might belong to Spirifer Kelhavii (V. Buch) found at Bear Island, and published in 

 the 'Memoirs of the Academy of Sciences of Berlin,' in 1846 ; but the shell there delineated 

 is so very much more elongated than any British example I have seen, that I should not 

 feel myself authorised to attribute to it our English shells without having been able to 

 examine some specimens of the Prussian author's species. 



Loc. Professor M'Coy states that his specimens (now in the Cambridge Museum) are 

 from Derbyshire ; it abounds at Park Hill, Longnor, whence a beautiful series may 

 be seen in the Museum of the Geological Survey, as well as the British Museum ; and I 

 have received the loan of several fine examples obtained at Bolland and the Isle of Man, 

 from Messrs. E. Wood, Parker, and Muschen, and the Rev. Dr. Cumming. Professor 

 M'Coy states the shell to be common in the Irish limestone at Ardagh. It has often been 

 erroneously labelled JSp. triangularis in various collections. 



