Dr. BiGSBY on the Geography and Geology of Lake Huron. 203 



stonCj or with quartz^ having carious holes or cavities, lined with rock crystal. 

 The substance of the coral itself is silex, with a slight calcareous admixture. 

 Including all the species, I have seen sixty specimens of this fossil; but in no 

 instance has either the base of the attachment, or the upper extremity of the 

 column, been preserved. The greatest length of any column that I have seen 

 is 27 inches. The columns are not found in groups, but single, mixed with 

 turbinoliae, chain-coral, encrinites, &c. 



Species II. PI. XXVIII. fig. 1. — This species is the largest. The greatest 

 length that I have seen in any joint has been If in.; of which the diameter 

 at the base was If in. The greatest diameter I have seen at the base of any 

 joint, has been 2f in., the length of the joint being If in. The upper part of 

 each joint is much less inflated in this than in the first species. 



Species III. fig. 3. — In this species, which is the smallest I have met with, 

 the column tapers more rapidly, the upper part of each joint is more enlarged, 

 and is greater in proportion to the rest of the joint, than in the two foregoing 

 species. 



Species IV. fig. 4. — In this species the plane passing through the line of 

 the base of each joint, is oblique to the axis of the column. 



Species V. fig. 5. — In this species the cyhndrical part of each joint disap- 

 pears, and the joint assumes the form of an oblate spheroid. 



Many other species of coral are also met with in Drummond Island. 

 Of astreffi I have seen six or seven species, one of them considerably resem- 

 bling the lithostrotion of Llywd. 



Of the genus Porites, or madreporae of Lamarck, one species. 

 Of Caryophyllia one species, which merits a more detailed notice. It is re- 

 presented in PI. XXIX. figures I and 2. The former figure shows the 

 outside and the base of the coral, and exhibits a peculiarity which is quite 

 new, I believe, to corals of this genus. Tubes appear branching from the 

 outside, and communicating with the interior. Most of these are broken off; 

 but one of them remains, which is three-fourths of an inch long, and takes an 

 ascending direction. In fig. 2, tubes are seen near the base, which take the 

 contrary direction. It is difficult to imagine what purpose these branches could 

 serve in the former case ; but in the latter they might assist in strengthening 

 the base of attachment of the coral. I have in my possession a specimen 

 from Collier's Harbour, containing a group of eleven of these corals, closely 

 crowded together. 



Turbinoliae abound in Drummond. The different species vary in size, from 

 5 in. to 10 in. in length; the larger being sometimes 4 inches broad at the 

 upper end. I have seen 21 of these corals in one mass, each 10 inches long. 



