154 Silurian Fossils of Nova Scotia. 



25. MuRCHisoNiA Arisaigensis. N. sp. 



Shell teretely conical, volutions about five, gradually increasing 

 from the apex, rounded with a slight angulation or carina in the 

 middle. The surface is unknown and the angular band on the 

 volution is the only means of determining its generic rela- 

 tions. 



This differs from any of the described species of Murchisonia 

 from American localities. 



26. Murchisonia aciCulata. N. sp. 



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 ; volu- 

 tions marked by a distinct band along the centre, and a sub-sutu- 

 ral carina marking the upper side of the volutions; surface 



striated. 



Fig. 13. Fig. 15. 



Fig. U. 



ii 



2?. HoLOPEA REVERSA. N. sp. Fig. 14. 



Shell small, sinistral ; spire depressed, volutions about three ; 

 the two first small and gradually expanding, the last one rapidly 

 expanding and ventricose ; aperture wide expanded ; suture im- 

 pressed. Surface unknown. 



This shell has the general form of Holopea, but I have seen 

 only a single specimen, which is a cast. It is remarkable and 

 readily recognised from the sinistral spire. 



28. Orthoceras punctostriatum. N. sp. Fig. 15. 



Shell slender, very gradually tapering, almost cylindrical; 

 Septa distant about one third the diameter. Siph uncle central; 

 section circular. Surface very finely striated with unequal undu- 

 lating strisG, the interstices between which, are punctse which are 

 oblong indentations often becoming confluent. 



