193 



Professor Agassiz remarked of the rock in which this spe- 

 cimen occurred, that it was the oldest member of the terti- 

 ary group, if not, as some supposed, belonging to the cre- 

 taceous ; the name of Pisolttic system had been applied to 

 it by Elie de Beaumont. 



He also pointed out the characters in which his genus 

 Pygorhynchus differs from Clypeaster and Echinolampas. 



Both have the ambulacra petaloid, an anterior mouth, and 

 posterior anus. Echinolampas has no teeth, and the interior of 

 the body is a simple caviiy. Clypeaster has five teeth, and the 

 internal cavity divided by columns. Pygorhynchus is distin- 

 guished by a depression at the anus, the ambulacra elongated and 

 distinct to the margin. The mouth is transverse, but in the other 

 genera direct. He pronounces the species exhibited by Mr. 

 Bouve decidedly new. 



Dr. W. F. Channing gave an account of the Crawfish 

 from the Mammoth Cave, Kentucky, presented by him at 

 the last meeting. 



He remarked that, like everything else having life in the cave, 

 it was colorless. There were points, in the ordinary position of 

 the eyes, which might prove to be those organs or their rudi- 

 ments. A Crawfish of the common species was caught in the 

 cave at nearly the same time as the present specimen, having 

 undoubtedly entered during a flood of Green River, which oc- 

 curred at the time, and during which the waters back up into 

 the cave. This would explain, perhaps, the original introduc- 

 tion both of the blind fish and of the crawfish, but would make it 

 remarkable that the species had continued distinct. 



Professor Agassiz had examined the Crawfish presented 

 by Dr. Channing. 



The eye of this class of Crustaceans is placed upon a pedicle, 

 and appears like a bulb covered with facets. In this specimen 

 the pedicle exists, but the bulb with facets is wanting; and con- 

 sequently there is no eye, though he supposed the eye to exist in 

 a rudimentary state ; but the specimen was not in a state to admit 

 of ascertaining whether or not the optic nerve existed. The 



PROCEEDINGS B. S. N. H. 18 MARCH, ld-17. 



