SPIRIPERA. 41 



greatest width of the shell, cardinal angles rounded; valves moderately convex; area 

 triangular, rather elevated ; fissure large ; beak small and incurved. Each valve is 

 ornamented by from seventeen to twenty-three radiating ribs, of which three smaller ones 

 occupy the mesial fold of the dorsal valve, which is but moderately elevated, and longitu- 

 dinally flattened along its middle. In the ventral valve the sinus is rather deep, and 

 exhibits also two or three smaller ribs. The frontal wave is strongly marked ; the ribs 

 are intersected in both valves by concentric laminae of growth. The dimensions of 

 Sowerby's two original examples have given — 



Length 7, width 8, depth 6 lines. 

 6, „ 7, „ 4£ lines. 



Obs. The only specimens I have been able to examine are those figured in the 

 ' Mineral Conchology,' and from such scanty material I would hardly consider myself 

 warranted to offer any decided opinion as to their specific claims. After comparing the 

 specimens with the originals of S. octopiicata, the differences consisted in the last-named 

 shell being larger and more transverse, with fewer and bolder ribs ; there exists also a 

 dissimilarity in the character of the mesial fold, which is, in S. minima, much flatter 

 and more regularly divided into three flattened ribs, than in any examples of true 

 octopiicata that have passed under my notice. It is, therefore, probable that after a more 

 extended examination of a larger number of specimens these slight differences may be con- 

 sidered valueless, and that it may be found desirable to add it also to the varieties of 

 Sp. cristata of Schlotheim. 



Professor M'Coy is, however, mistaken when he describes the shell under description 

 as possessing an angular mesial fold or ridge, this last being most distinctly flattened in 

 the two original examples preserved in the collection of Mr. J. de C. Sowerby, and which 

 I have drawn afresh under figs. 56 and 59 of my plate. For similar reasons I must object 

 to the identification of the shell in question, as proposed by Mr. Morris, 1 with Anomites 

 acutus of Martin, which seems to me much more probably the young of some other 

 species. 



Loc. Sowerby's specimens were obtained, along with others of Athyris ambiguus, in 

 decomposed limestone near Bakewell ; the shell being silicefied. 



Spiriferina (?) partita, Portlock. 2 Plate VII, figs. 60, 61. 



Spirifera partita, Portlock. Report on the Geology of the County of Londonderry, 

 Tyrone, and Fermanagh, p. 567, pi. xxxviii, fig. 3, 1843. 



"Spec. Char. A small shell, 2" long and 35" wide; dorsal valve {our ventral one) with 



1 'A Catalogue of British Fossils,' p. 150, 1854. 



2 Not having been able to procure a specimen of the above-named shell, and as the description and 

 illustrations are not sufficiently detailed to allow of my forming a positive opinion as to its specific claims 

 and affinities, I have preferred to simply reproduce Colonel Portlock's description and figures. 



6 



