268 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY. 
of the muscles directly belonging to the reduced portion, and with 
greater development of the muscles in front of it. And, finally, the 
probability that the rattlesnakes represent at least two lines of descent 
may be added ; one, that of Sistrurus, more closely connected with the 
Copperheads; another, that of Crotalus durissus and allies, connecting 
with that of Lachests mutus. 
Aprix 16, 1888. 
LIST OF DIAGRAMS. 
PLATE I. 
2. Sistrurus catenatus. 4 times nat. 
4. Sistrurus catenatus. 3} times nat. 
6. Crotalus confluentus. 2 times nat. 
Crotalus horridus. Nat. size. 
. PLATE II. 
Fig. 8. Crotalus horridus. Nat. size. 
9, 10. Rhinocerophis ammodytoides. 2} times nat. 
11. Lachesis mutus. 3 times nat. 
12. Halysacutus. After Giinther. 
18. Ancistrodon piscivorus. 2 times nat. 
14. Ancistrodon contortrix. 2} times nat. 
