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



merits to Sir James Macgregor, and to Dr. Wright (Inspector of Hospitals)^ 

 for their zealous aid, afforded to me when prosecuting these researches. — 

 Mr. M. White of the Army Medical Staff will also accept of my best thanks 

 for various acts of kindness. Mr. Parkinson and Mr. C. Stokes have most 

 obligingly given me free access to their libraries and collections. 



APPENDIX. 



I. On a Trilohite from Lake Huron. 



BY CHARLES STOKES^ ESQ. 



" In breaking away the rock from a specimen of trilohite found at St. Jo- 

 seph, and now in my possession, a fortunate fracture exposed a small part of 

 the under side of the fossil ; and encouraged me, as the rock was of a favour- 

 able texture, and the fossil in a good state of preservation, to attempt a further 

 dissection, in the hope of laying open some parts of the animal with which we 

 have hitherto been unacquainted ; and I discovered the part forming the en- 

 trance into the stomach. Its structure, which considerably resembles that of 

 the analogous parts in some recent crabs, will be best explained by the accom- 

 panying drawing (PI. XXVII. fig. 1. b.). I have frequently attempted to cut 

 away the rock from specimens of trilohite from Dudley ; but owing to its hard- 

 ness, I have not yet succeeded in developing any thing similar." 



II. List of some of the Recent Shells of Lake Huron. 



I am obliged to I. E. Gray, Esq. of Burton-street, Burton Crescent, for the 

 names of some recent shells which I collected in Lake Huron. 



Helix albolabris, . . Say Amer. Conchol. T. i. fig. I. 



alternata, . . T. i. fig. 2. 



angulata ? . . Rackett Linn. Trans, vol. xiii. 



Planorbis trivalva, . . Say Amer. Conchol. T. ii.fig. 2. 



Lymnaea Catascopium, T. iii. fig. 3. 



heterostropha, T. i. fig. 6. 



(Nov. Spec). 



Physa (Nov. Spec). 



Valvata (Nov. Spec) 



Cyclostoma tricarinata. Say Amer. Conchol. 



Cyclas (Nov. Spec). 



