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 Crotatus durissus and allies, connecting 

 with that of Lachesis mutus. 



ApKiL 16, 1888. 



LIST OF DIAGRAMS. 



PLATE I. 



Figs. 1, 2. Sistrurus catenatus. 4 times nat. 



3, 4. Sistrurus catenatus. 3^ times nat. 



6, 6. Crotalus confluentus. 2 times nat. 



7. 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. Halys acutus. After Giinther. 



13. Ancistrodon piscivorus. 2 times nat. 



14. Ancistrodon contortrix. 2^ times nat. 



