1885.] NATURAL SCIENCES OF PHILADELPHIA. 139 



with their most salient marks of distinction, 1 shall now proceed 

 to tabulate. 



Synopsis of Species. 



I. Nostrils lateral ; opening on the anterior extremity of the 



superciliary ridge. 



A. A single row of pyramidal scales at the periphery of the 



abdomen ; gular scales subequal; abdominal scales smooth. 



1. Cephalic spines very short and tubercular ; oceipitals less 



prolonged than the longest of the temporals, posteri- 

 orly ; head broader than long. • Douglassi. 1. 



2. Cephalic spines of medium length ; occipital spines 



directed obliquely upwards, and a little less prolonged 

 than the longest of the temporals, posteriorly ; head 

 broader than long. Boucardi. 2. 



3. Cephalic spines of medium length ; occipital spines hori- 



zontal, more prolonged than the longest of the tempor- 

 als, posteriorly ; head as broad as long, orbicular e. 3. 



B. Two rows of pyramidal scales at the periphery of the abdo- 



men ; three or four rows of enlarged pointed gular scales 

 upon each side of the median line. 



1. Abdominal scales smooth ; cephalic spines to the number 



of twelve or thirteen ; occipital spines horizontal or 

 nearly so. coronatum. i. 



2. Abdominal scales carinated ; cephalic spines eight in 



number; occipital spines vertical. asio. 5. 



II. Nostrils anterior ; situated within the superciliary ridge ; two 



rows of enlarged gular scales, one row on each side of, and 

 distant from, the median line. 

 A. Two rows of pyramidal scales at the periphery of the abdo- 

 men ; auricular opening conspicuous. 



1. Abdominal scales carinated, sometimes smooth or nearly 



so ; occipital spines directed obliquely backward, much 

 longer than the longest of the temporals, from which 

 they are separated by one or two flattened scales. 



cornutum. 6. 



2. Abdominal scales carinated ; cephalic spines forming with 



the inframaxillary plates a continuous circular series ; 

 occipital spines projecting posteriorly as far as, and 

 not separated from, the longest of the temporals. 



regale. 1. 



