denotes the male, while at the breeding season, male frogs have the 

 brush and pad upon the thumb, and male toads have corneous glands 

 upon their fingers. Among serpents the females are larger, thicker, 

 less active, and duller colored than the males The difference in size 

 is quite pronounced, especially when the abdomen is filled with eggs. 

 At such times the appearance of the animal is strikingly changed, it 

 being much enlarged, thicker, and of duller coloration than at other 

 periods. The tip of the tail is thinner in males than in females, and 

 its base somewhat enlarged, in order to lodge the double infcromittent 

 organ. The young are also bright colored. 



Observations upon the development of the rattlesnake show the value 

 of certain characters used in classification. Thus, the foetal Crotcdoph- 

 orus has the subcaudal plates or urosteges divided, and is also pro- 

 vided with grooved fangs. We thus see that these characters indicate 

 immaturity, and hence it follows that those serpents with entire ui'os- 

 teges, and with the fangs perforated, other tilings being equal, rank 

 higher than those ia which these foetal conditions are permanent m 

 the adult state. 



The materials upon which the accompanying list is founded are 

 the specimens in the Museum of Michigan University, and those col- 

 lected by the writer and other persons in their rambles through the 

 woods. The author has received assistance of this latter kind from 

 Mr. C. B. Cochran and D. J. and W. K. Higley. The last named gen- 

 tleman has also aided him somewhat in preparing the list of 

 Museum specimens. However, the writer considers himself responsi- 

 ble for the correctness of the present Kst, he having personally verified 

 every identification. Where this was not possible, and the opportunity 

 of seeing the animal not afforded, the name has been inserted with 

 quotation marks. A star prefixed to a name indicates that the animal 

 was observed in the vicinity of Ann Arbor, and a question mark thus 

 placed signifies that though recorded from the State by some author, 

 yet, in the judgment of the present writer, it is doubtful whether such 

 animal belongs to our fauna ; and while the name is here given for 

 reference, the question is raised as to whether the herpetologist so re- 

 ferring it has not fallen into an error. 



Of Amphibia and EeptUia not yet observed in Michigan, but whose 

 geographical range is such as to render their occurrence in our limits 

 not improbable, may be mentioned ; Spelerpes lilineatus, longicaudus, 

 et niter, Bana septentrional is* Eutcenia proxima, and Ophiholus calli- 

 gaster. 



*Proc. Acad. Nat. Sci., Phil., 1851, p. Gl. 



