562 MISS J. DONALD ON NEW AND LITTLE-KNOWN 



41. Notes on some New and Little-Known Species of Cakbo- 

 NiFEROTJS Mtjecsisonia. By Miss Jane Donald. (Communi- 

 cated by J". G. GooDCHiLD, Esq., P.G.S. Eead June 22nd, 

 1892.) 



[Plates XVI. & XVII.] 



EvEKT student of the Carboniferous rocks must be struck by the 

 number of keeled gasteropoda they contain, many of which are so 

 small and also so strongly resemble one another that only the study 

 and comparison of a large series can afford means for anything like 

 an accurate determination of different species. As a help towards 

 their elucidation, I am about to figure and define the characteristics 

 of some of the more marked forms of Murchisonia. Several of these 

 have been previously described, but I think it well to reproduce 

 them with more detailed notes. 



In a previous paper ^ the various sections into which it has been 

 considered advisable to group different species of Murchisonia have 

 been noticed. Of the species here described two alone can un- 

 doubtedly be referred to Goniostropha, (Ehl., as possessing the 

 characteristics of that section : namely, the turriculated form, 

 angular whorls, and sinual band situated on the summit of the 

 angle. In M. quadricarinata, M. quinquecarinata, M. elongata, 

 M. KirJcbyi, M. plana, and M. conula, var. convecca, the sinus is 

 situated above the angle; in other respects these shells resemble 

 species of Goniostropha. It is therefore a question whether they 

 should be referred to that section or whether the position of the 

 sinual band be considered suflBciently distinctive to necessitate 

 their being grouped together in a new section. In the latter alter- 

 native I should suggest the name Hypergonia, and take M. quadri- 

 carinata for the type. 



With regard to M. pentonensis, it is somewhat difficult to decide 

 whether the sinual band is actually on the summit of the angle or 

 immediately above. I incline to the latter opinion, and should 

 therefore group this species with M. quadricarinata and allied 

 forms. M. conida, var. conveoca, and M. plana differ from the 

 other species of this group, and also from species of Goniostropha, in 

 having the base of the shell flattened. M. amcena, De Kon., agrees 

 with these two last-named species in having the sinus above the 

 angle and also in the base being flattened. The possession of this 

 flattened base is hardly a characteristic of such value as to render 

 it necessary to separate these shells from those referred to Hyper- 

 gonia. In addition to these keeled Murchisonice, I notice a new 

 and interesting smooth form, probably belonging to the section 

 Coelocaulus, CEhl. I also give a fuller description of a fossil de- 

 scribed in 1859 by Prof. Haughton^ as Cerithioides telescopium, 



^ ' Descr. of some New Species of Carb. Gasteropoda,' Quart. Journ. Geol. 

 Soe. vol. xlv. (1889) p. 621. 



^ ' On some Fossil Pyraraidellidse from the Garb. Limestone of Cork and 

 Clonmel,' Proe. Dublin University Zool. and Bot. Assoc, vol. i. pt. iii. p. 282, 

 pi. XX. figs. 2-4. 



