16 PROCEEDINGS OF THE AC.VDEMY OF [Jan., 



COLUBRID^/ 

 Key to the Genera. 



I. aglypha;: 



A. — Posterior dorsal hypapopliyses present: 



a. — Maxillary teeth longer bsliiml; scales keeled: 



a\ — Anal entire; no scale pits, .... EaT^ESiA. 

 _^ 6\ — Anal divided: 



2 interaasals; scale pits present, 



Tropidonotus. 

 2 internasals; no scale pits; keeled only on tail, 



Semixatrix. 

 1 internasal; no scale pits; keeled only on tail, 



Helicops. 

 h.- Maxillary teeth equal; scales keeled: 



a}. — Anal entire, Tropidocloxium. 



h^. — 'Anal divided: 



cr. — Loreal absent, Storeria. 



h'. — Loreal present : 



a\— 1 nasal; 1 preocular, . . Clonophis. 

 i\ — 2 nasals; preocular absent: 



2 internasals, .... Amphiardis. 



1 internasal, Haldea. 



B. — Posterior dorsal hypapopliyses absent : 

 ' a. — Maxillary teeth equal, or nearly so: 

 a\ — Anal entire: 



a^ — Scales smooth ; size large: 



Snout normal; scales less than 17 rows, 



Spilotes. 

 Snout elongate ; scales more than 25 rows, 



RHINECIIId. 



h"^. — Scales smooth; size small and slender; no 

 loreal ; pre- and postfrontals touching labials, 



Stilosoma. 

 C-. — Scales keeled; size large; 4-6 prefrontals, 



PiTYOPHIS. 



6\ — Anal divided: 



a\ — Scales keeled: 



2 nasals; size large; spotted or striped, 



Coluber. 

 1 nasal; size small; color green, 



Cyclophis. 



• Although not strictly followed here, the plan of serial arrangement of the 

 genera of C'o?«6/'i(Z(e adopted by Mr. Boulenger possesses a decided advan- 

 tage, ia that it does not pretend to a knowledge of close affinities which we 

 have not gained. 



