66 Proceedings of the Royal Physical Society. 



whorl. As thus restricted, the following Scotch species are 

 here comprised — Uuomphalus j^entangtclatus (Shy.), E. acutus 

 (Sby.), and, I presume, E. marginatus (M'Coy). 



The next division instituted by Professor de Koninck is 

 Phymatifer* in which the form is discoid, no spiral keel, but 

 the upper surface of the whorls and sometimes the lower 

 ornamented with rounded tubercles. This section would 

 comprise Phymatifer (Euomph.) pitgilis (PhilL), and perhaps 

 P. (Euomjjh.) tuherctdaMs (FlemiDg). For the next group the 

 genus Schizostoma (Bronn)-|- has been adopted, and comprises 

 those shells similar in form and general character to Euom- 

 phahcs proper, but the body whorl bi-carinated, one keel 

 placed on the upper, the other on the lower surface ; the 

 Scotch type of this group will be Schizostoma (Euomph.) 

 calyx (Phill.), and it will also include S. (Euomph.) carhonarius 

 (M'Coy). 



The value of these sections entirely depends upon the 

 stability of the characters of the species placed in them. 

 The group Phymatifer will probably form a good section, but 

 the separation of Euomphalus and Schizostoma is, unless the 

 specimens are very well preserved, difficult to accomplish, 

 especially in so far as the uni- and bi-carinated nature of the 

 whorls is concerned. Lastly, I believe, we have a further 

 section of this group of shells in Meek's Omphalotrochus, a 

 massive tabular shell in which will probably be included 

 the large Euomphalus tabulatus. 



The genus Raphistoma (Hall) has hitherto been supposed 

 to be entirely Silurian, but Professor de Koninck now 

 employs it for some Carboniferous Univalves, amongst which 

 may be mentioned Euomphalus radians^ occurring both 

 in this country and Belgium. The group Euomphalus is 

 remarkable for the camerated nature of the shell, a feature 

 often beautifully shown in polished sections of E. pentangu- 

 latus. One of the least common species met with in the 

 Carboniferous rocks of Scotland is probably the Euomphalus 

 crotalostomus (M'Coy) found by Mr J. Linn in the Bathgate 

 limestone.! This also appertains, I am inclined to believe, 



* Gasteropodes, p. 1-19. f Ibid., p. 152. 



t"On some of the less common liutligatc Fossils" (Traus. Gcol. Soc, 

 Ediub., 1873, ii., pt. 2, p. 192). 



