96 [July 20, 
Cope. ]} 
A few rows of large scales on the collar, of which the marginal is the 
largest ; two preoculars and a frenodcular; four supraorbitals ; similar to 
C. communis, but head shorter and scuta wider; brown with black cross- 
bands on sides, which join across the middle line on the lumbar region ; 
sacral region and femora white spotted. 
The short head of this species is accompanied by an abbreviation of the 
sutures of mutual contact of the fronto-nasal and internasal pairs of scuta, 
which is not seen in the other allied species. The unique specimen is 
smaller than the females of the two species last described, yet it presents 
no trace of stripes. From its coloration I should suppose it to be an adult 
male. 
The locality of this specimen is only stated to be ‘* Mexico.’ 
b] 
GERRHONOTID 2. 
The important variations in the scutellation of the head of the species 
of this family lead to the view that several genera are indicated. The 
definitions of these are as clear as those of many genera of the system, and 
as it appears to me, may be profitably associated with names as elsewhere. 
There is a tendency to subdivision of the head-shields in some species, it 
is true, but a little patience in studying the homologies of the portions 
separated in excess, will refer them to their proper positions and reduce 
them to the types herein mentioned. Dr. Gray, in 1845, attempted to 
distinguish four genera among the species of the original genus Gerrhono- 
tus of Wiegmann, but the characters he seized upon do not, with one ex- 
ception, possess the importance he attached to them. The exception is 
that of Barissta, which has maintained its distinctive feature, the absence 
of the interfrontonasal scutum. Two species recently described by 
Bocourt exhibit, according to that herpetologist, the equally important 
feature of the absence of the frontonasal plates. The great subdivision of 
the plates of the internasal region distinguishes a number of species, one 
of which was named long since Pterogasterus by Messrs. Peale and Green. 
PTEROGASTERUS Peale and Green. 
Three pairs of internasal scuta; interfrontonasals and frontonasals 
present. 2 
Species: P. ventralis P. & G.; P. tessellatus Wiegm.; P. ophiurus 
Cope; P. infernalis B. & G.; P. lemniscatus Boc.; P. modestus Cope, 
sp. nov. 
GERRHONOTUS Wiegmann. 
Two pairs of internasals ; interfrontonasals and frontonasals present. 
Species: G. multicarinatus Blv.; G. grandis B. & G.; G. seincicaudus 
Skilt.; G. principis B. & G.; G. kingii Gray; G. gramineus Cope; G. 
auritus Cope; G. teniatus Wiegm.; G. deppet Wiegm.; G. formosus Bd.; 
G. vasconcelosti Boc.; G. rhombifer Pet.; G. monticolus Cope, sp. nov. 
Mesaspis Cope, gen. nov. 
Two pairs of internasals ; interfrontonasal present; frontonasals want- 
ing. 
Species: M. moreletii Boc.; M. fulous Boe. 
