204 Dr. BiGSBY on the Geography and Geology of Lake Huron. 



One species^ which is common, resembles that from Italy figured in Par- 

 kinson's Organic Remains, pi. iv. fig. 9. — Plate XXIX. fig. 3. represents the 

 smallest species. Figure 4 is remarkable for the spiral curvature around the 

 centre of the radiating lamellae. Other species are represented in figures 

 5 and 6. 



The chain-coral (Tubipora catenula, Gmelin ; Catenipora escharoides, La- 

 marck) is common ; as also the Tubipora Strues, Park. Org. Rem. pi. ii. fig. 1, 

 and Tubipora ramosa. Ibid. pi. iii. fig. I. 



Small retiporae, and milleporae, are abundant. 



Of shells there are many species of terebratulae found near Collier's Har- 

 bour, and a large species is common near the True Detour, and in the cliffs 

 near the False Detour, where it is accompanied with ammonites. 



Of orthocerae there are some remains ; but they are not so abundant in 

 Drummond as in St. Joseph's or Thessalon Islands. Among them one spe- 

 cies has a considerable resemblance to O. annulata of Sowerby. PI. XXX. 

 figures I and 2, represent two fragments, which resemble those figured in 

 Breynius's Dissertatio de Polythalamiis, tab. 6, fig. I and 2. 



Another class of fossils from Collier's Harbour differs from any thing I have 

 seen. They are columns, usually tapering rapidly, composed of circular discs, 

 with rounded edges, placed one upon the other. Each disc is from ^ to ^ in. 

 thick, and from 5 to 2 in. in diameter. They vary much among themselves. 

 Thus PI. XXX. fig. 5, is of considerable length, and tapers very gradually. 

 In fig. 3 the diminution is rapid. In fig. 4 there is a sudden diminution from a 

 large to a small size. In fig. 6 the column is curved ; in fig. 7 the discs are 

 placed obliquely. 



The entrochites mentioned among the organic remains of St. Joseph and the 

 north occur in Drummond also, but sometimes of twice the size. The Penta- 

 crinite is also met with. 



The Little Manitou, in addition to the turbinoliae, and most of the other 

 corals of Drummond Island, possesses several species of organic remains, 

 which are found no where else throughout the Manitouhne chain. They 

 occur in the knotty stratum : but as they are but obscurely defined, I shall pass 

 them over. 



On the Foreign and Native Debris of Lake Huron. 



The shores and bed of Lake Huron appear to have been subjected to the 

 violent action of a flood of waters and floating substances rushing from the 

 north. That such a flood did happen is proved, not only by the abraded state 

 of the surface of the northern mainland and scattered isles of the Manitou- 



