454 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4rH Ser. 
EXPLANATION OF PLATE XXVIII 
Fig. 1. Crotalus cerastes Hallowell—Section of skin. 
Fig. 2. Crotalus lepidus Kennicott—Section of skin. 
Fig. 3. Crotalus pricei Van Denburgh—Section of skin. 
