226 BRITISH CARBONIFEROUS BRACHIOPODA. 



Spirifera ellipitica, Phillips (p. 63). Figs. 1 — 3. 



1 am not quite satisfied of having been correct while placing this species ? among 

 the varieties of S. lincata, its general transverse form being very constant, as far as I have 

 hitherto seen. 



Spiriferina cristata, Schloiheim, var. octoplicata Soto. (p. 38). Plate VII, figs. 37 — 47, 

 and 00, 01 ; and Plate LII, figs. 9, 10, and 13. 



This is certainly a very variable species. In the generality of specimens the mesial 

 fold is composed of a single rib, which is much larger than those situated on the lateral 

 portions of the shell ; its crest is sometimes evenly rounded in all its length, but, as I 

 have already described, becomes in many cases flattened, and even slightly longitudinally 

 depressed as it approaches the frontal margin. Subsequently to my description of this 

 interesting species, I became completely satisfied that S. partita, Portlock (p. 41, 

 PI. VII, figs. GO, 61) would require to be located among the synonyms of the species 

 under description, and another remarkable modification has turned up, which I have 

 distinguished by the varietal designation of biplicata (PI. LII, figs. 11, 12). This variety, of 

 which many examples have been found by Mr. Burrow in the lower scar limestone of 

 Settle, in Yorkshire, and by Prof. Harkness in that of Little Island, near Cork, in 

 Ireland, has the usual shape and character of Sp. cristata, or of its large carboniferous 

 variety ocfoplicata ; it presents also, according to the specimens, the same variable number of 

 lateral ribs, viz., four, five, and eight, on the lateral portions of the shell, but the fold is no 

 longer simply rounded or flattened, as in the typical shapes of Sp. cristata, but divided 

 into two distinct ribs by a sulcus of variable depth ; a well-marked rib extending likewise 

 along the middle of the sinus, as seen in the illustrations above mentioned. That this is 

 nothing more than a modification of the more general shape of Schlotheim's species is 

 clearly proved by the many intermediate gradations in form which connect the specimens 

 with rounded sinus to those with biplicated ones. In PI. LII, fig. 9 represents a specimen 

 of Sp. cristata with a more than usual angular fold ; fig. 10 shows the fold slightly flattened 

 along its crest, and divided by a slight groove, while in figs. 11 and 12 it is so much 

 deepened as to divide the fold into two ribs. Very rarely indeed, but still as an exception, 

 the fold has become triplicated towards the front, a fact which was not overlooked by 

 Sowerby, since a specimen so conditioned is figured by that author along with his type- 

 shapes of Sp. octoplicata, PI. LII, fig. 13. The largest example of the var. biplicata 

 that has come under my notice measured — 

 Length 1 2, width 1 5, depth 9 lines. 



