FOSSILS. GO 5 



angular band on the volution is the only means of determining its 

 generic relations. 



This differs from any of the described species of Murchisonia from 

 American localities. Arisaig, coll. J. W. D. 



Murchisonia aciculata, Hall. Shell slender, very gradually tapering, 

 volutions about six or seven, the last ones moderately ventricose, 

 aperture elongate-oval or ovate, rounded at the anterior margin, 

 columella plain ; volutions marked by a distinct band along the 

 centre, and a sub-sutural carina marking the upper side of the volu- 

 tions ; surface striated. Arisaig, coll. J. W. D. 



Pleurotomaria. A flat species with four turns. Arisaig, Dr Honey- 

 man. Nictaux, J. W. D. 



Holopea reversa, Hall (Fig. 211). Shell small, sinistral; spire 

 depressed, volutions about three ; the two first small and gradually 

 expanding, the last one rapidly expanding and ventri- „. „., 

 cose ; aperture wide expanded ; suture impressed. Sur- 

 face unknown. This shell has the general form of Holo- 

 pea, but I have seen only a single specimen, which is a 

 cast. It is remarkable and readily recognised from the sinistral spire. 

 Arisaig, coll. J. W. D. 



Bucania trilobita, Hall. Arisaig, East River, Nictaux, coll. J. W. D. 



Bellerophon expansus (?), Sow. Arisaig, Dr Honeyraan. 



Bellerophon carinatus^ Sow. Arisaig, Dr Honeyman. 



Platyachisrna helicites, Sow. Arisaig, Dr Honeyman. 



Acroculia helicites, Sow. Arisaig, Dr Honeyman. This and the 

 three last species are from the lists of Dr Honeyman and Mr Salter. 



Orthoceras punctostriatum^ Hall (Fig, 212). Shell slender, very 

 gradually tapering, almost cylindrical. Septa distant about one-third 

 the diameter. Siphuncle central ; section circular. Surface very 

 finely striated with unequal undulating stride, the interstices between 

 which are punctse, which are oblong indentations often becoming 

 confluent. 



Fig. 212. Orthoceras punctostnahan. Fig. 213. 0. elegantuhim, and foition magnified. 



This species is remarkable for its extremely gently tapering form ; 

 the fragment of more than an inch long, showing scarcely a per- 

 ceptible diminution in diameter. There are twelve and a half chain- 



