260 Proceedings of the Royal Physical Society. 



Murchisonid ? 

 The specimens preserved in the calcareous sandstone just referred to, 

 still retain part of the shell-substance, but corrosion has removed the 

 surface features which play such an important part in the classification. 

 All the specimens seem referable to a single species characterised by the 

 shape of the shell, which is high, with numerous whorls. The general 

 aspect is between that of Hormotoma and that of Turritoma, the whorls 

 being flatter than in the former, and yet not so flat as in Turritoma. 

 Taking the shape alone into consideration, these specimens bear a stronger 

 resemblance to Catozone Perner, than to any other Murchisonids. 1 



Pycnomphalus solarioides (Hall). 



1852. Pleurotomaria solarioides, Hall, Pal. New York, vol. ii., p. 348, pi. 84, tig. 4b. 

 1895. Pycnomphalus solarioides, Wliiteaves, Geological Survey of Canada, Palasozoic 

 Fossils, vol. iii., part ii., p. 88., pi. 13, figs. 3-8. 



This species is so well characterised by its depressed spire that it 



could hardly be confounded with any other North American Upper Silurian 



Pleurotomarids, and as the specimen at hand, though indifferently preserved, 



shows the main features of P. solarioides as delineated by Hall, Nicholson, 



and Whiteaves, it can be referred to it without much hesitation. It must 



however be admitted that such a specimen, if unaccompanied by other 



typically Upper Silurian forms, would have been difficult to identify. 



since certain Ordovician Gasteropods — Liospira for instance — may have 



a similar outline. 



Pleurotomarid. 



A trochiform shell, which may possibly belong to Lophospira or to 

 Trochonema, has angular carinated whorls not unlike Pleurotomaria 

 subdepressa Hall, which differs in being sinistral. 



Straparolhis ? sp. 



A minute discoidal shell of three volutions and only 2 mm. in diameter, 

 may belong to Straparollus, but its small size precludes a satisfactory 

 determination. It seems to possess a character occasionally met with in 

 the Euomphalidce, viz. septate inner whorls. 



Cephalopoda. 



Genus Discosorus Hall. 



1852. Discosorus, Hull, Pal. New York, vol. ii., p. 99. 



1888. Discosorus, Foord, Catalogue of the Fossil Cephalopoda in the British Museum 

 (Natural History), part i., p. 196. 



1 Systtme Silurien du Centre de la Bolihie, vol. iv. — " Gasteropodes," tome ii., 1907, p. 108. 



