392 
GEOLOGY OF THE SECOND DISTRICT. 
SO detaching the stony matter from the inferior surface, as to show its legs, or the divisions 
of its abdomen. 
From all the facts which have been disclosed in relation to these animals, I see no objection 
to placing them in one family, and considering the recent crustacean which I have figured as 
a representative of the ancient race. Some difference in organization may be found, yet the 
general form and some of the habits are so nearly alike, that in considering them all as one 
family, our error will be but trifling. In conclusion, I would reiiiark that one important duty 
yet remains for geologists and naturalists, namely, to compare, more carefully than they have 
51 -et done, fossil with living bodies. 
Having stated the principal facts in relation to the localities of the crustaceans of the Tren¬ 
ton period, I shall now introduce the following cuts illustrative of the univalves which have 
been discovered in this rock. 
101 . 
1. Tiocholites aramonius. 3. Subulites elongata. 5. Bellerophon punctifrons. 
2. Pleurotomaria lenticularis. 4. Cyrtooeras filosum. C. Bellerophon bilobatus. 
No. 1, is a rare fossil in the trenton ; it has been found in the Mohawk valley, but it has 
not fallen under my notice in the Second district. 
No. 2, is quite abundant at Watertown, and is common in the sub-crystalline grey variety 
of this rock. This is a large individual. 
Nos. 2 and 3 (fig. 102, p. 393), are the same species, and are drawn of the usual size of the 
animal. 
