262 Proceedings of the Royal Physical Society. 



towards the apex. The segments are in a plane 65° to the axis ; their 

 contour is evenly protuberant, but somewhat asymmetrical on the convex 

 side, where the outline forms a sigmoidal curve. 



The other specimens were cut longitudinally. They do not exhibit 

 any internal characters not already known to exist in the genus. 



In D. conoideus Hall (op. cit. pi. 28, fig. 13), the rate of tapering is 

 more rapid, and the segments are thicker and not so oblique to the axis 

 as in the present species. From D. borealis, D. regularis differs in the 

 lesser degree of curvature, and in the evenly protuberant nature of the 

 segments, which are moreover not crowded near the apex. 



Discosorus sp. 



A single siphuncle; partly obscured by intractable matrix, resembles 



closely D. gracilis Foord (op. cit. p. 198, fig. 26), in the rate of tapering 



and degree of curvature, while it differs from it in the greater distance 



of the siphuncular segments from each other. The visible portion of the 



specimen is 9 cm. long, and sixteen segments occur within that distance, 



while as many as nineteen occur within 6| cm. in the specimen figured 



by Dr Foord. The segments are also more oblique to the axis than is 



the case in D. gracilis. 



Actinoceras sp. [Fig. 2]. 



A silicified fragment from which most of the shell has been removed 

 belongs to a rapidly tapering species with sub-lateral siphuncle. The 

 diameter of the siphuncle is about a third that of the shell. The 

 endosiphon and several tubuli are well shown in transverse aspect. 



The septa — of which nine occur within a distance of 30 mm. — exhibit 

 a puzzlin Mature probably due to a peculiar deposition of silica. In the 

 portion Rarest to the siphuncle, the siliceous partitions replacing the 

 septa di /ide into two leaves before reaching the shell, in such wise 

 that the lower leaf of a given " septum " unites with the upper leaf of 

 the "septum" below. This appearance is probably analogous with that 

 depicted by Barrande in a specimen of Actinoceras tohitei (Stokes) from 

 the Niagara Group of Drummond Island. 1 



CRUSTACEA. 



Ostracoda. 



Large species of Zeperditia occur in extraordinary abundance, their 

 carapaces and external moulds covering the surface of three small slabs 

 of the limestone containing the Brachiopods enumerated above. 



1 Syst&nu Silurien du Centre de la BohSme, vol. ii. — " Cdphalopodes," -1""' S6rie, 1870, 

 pi. 437, fig. 17. 



