10 University of California Publications in Zoology [Veou.9 
cornua at their middle and end. The posterior cornua are short 
and have their origin close to the middle cornua. 
The orbital cavities are very large. A supratemporal open- 
ing is present in all of the species studied except Anota maccalli. 
The posterior temporal openings vary greatly in size and shape. 
The nasal openings may be anterior or lateral. 
Vertebral Column: The proecoelous vertebrae lack the zygo- 
sphene articulation, although there are corresponding rudiment- 
ary processes. Only the cervical vertebrae possess intercentra. 
There are twenty pairs of ribs, the first pair and the last four 
or five pairs being short. The ribs from the second to the eighth 
vertebra articulate by cartilage to the sternal ribs. The two 
sacral vertebrae are partly fused. At least six to eight caudal 
vertebrae possess haemal arches, the remaining being rudi- 
mentary or vestigial. The neural spines are short but show in 
some species a tendeney to form a dorsal crest. Chevron bones 
are present from the fourth or fifth caudal vertebra to near the 
end of the tail. These bones are pecular in the lack of a 
symphysis. 
Pectoral Girdle: The thin supraseapulas are nearly as long 
as the scapulas and extend well over the back. A proscapular 
process is present on each scapula. The episternum is only 
slightly curved and extends but a short distance beyond the 
sternum on each side. The sternum is broad and has a large 
fontanelle. Two or three sternal ribs may articulate with the 
sternum and the xiphoid rods are connected with but one rib. In 
Phrynosoma platyrhinos the third pair of sternal ribs have their 
origin on the xiphoid rods and only two ribs articulate with the 
sternum. 
Pelvic Girdle: The ilia are stout and nearly vertical in posi- 
tion, whereas the pubes and ischia are slender and transverse, 
being separated by a large ischio-pubie foramen. At the 
symphysis the bones are connected by cartilage. Extending pos- 
teriorly from the symphysis and dorsally toward the vertebral 
column, is a slender rod-like cartilage. This cartilage, although 
not mentioned by Cope (1898), is found in each species. Not 
being able to find a name for it in literature it is here termed 
