24 



Guide to the Invertelrata. 



Huronia. posterior part. This genus, so far as at present known, is limited 



GALLERY to the Silurian rocks of North America. 

 VII. 



Wall- 

 case 8. 



Fig. 44. — Huronia vertebralis, Stokes. Niagara Group (Wenlock) : Druramond 

 Island, Lake Huron. From specimen presented by Dr. Big-sby. The 

 septa are added from Dr. Bigsby's drawing ; they were only indicated in 

 the specimen by "colourless lines on the brown limestone." (Much 

 reduced, after a drawing by Dr. S. P. Woodward.) 



Wall- 

 case 8. 



In the genus Piloceras the shell is conical and comparatively 

 short, and the siphuncle very large ; usually only the latter is 



Fig. 45. — Piloceras invaginatum, Salter. Durness Limestone : Sutherlandshire. 

 S, S, remains of septa ; Si, siphuncle, a little restored in the lower part, 

 with ridges marking the attachment of the septa. (One-half natural size.) 



preserved. It is found in North America, and in the British 

 Islands only in the Durness Limestone in Sutherlandshire. 



