EMERSON: ANATOMY OF TYPHLOMOLGE. 
49 
cartilaginous rods of the primordial skull and posteriorly the inner 
borders of the otic capsules form the sides. The foramen magnum 
is formed by the basi- and supra-occipital arches and the inner walls 
of the capsules. Between this and the neural arch of the first verte¬ 
bra, the spinal cord is protected dorsally by thick connective tissue. 
The frontals are long, thin, transparent bones, contiguous to one 
another in the mid-dorsal line. On the anterior part of the dorsal 
surface, each has a slightly roughened area, the articular surface for 
one of the posterior processes of the premaxillary. Along the outer 
edge of the ventral surface is a groove which partially invests the 
dorsal surface of the cartilaginous rod of the primordial skull, and 
near the posterior border is an articular surface for the parietal, 
which bone it partially overlaps. 
The parietals are somewhat shorter than the frontals, but resemble 
them closely in structure and relation to each other. On their 
ventral surfaces are deep grooves, continuous with those on the 
frontals, investing the rods of the chondrocranium. The postero¬ 
lateral angle of the parietal overlaps and articulates with the anterior 
portion of the otic capsules. 
The parabasal is the largest bone of the skull. It is a thin, flat 
plate, as long as the combined frontal and parietal. The posterior 
portion is broad and nearly square and the anterior is very long and, 
somewhat narrower, tapering slightly to the anterior border which is 
bilobed. The ventral surface is smooth, except antero-laterally where 
it is slightly roughened, articulating with the dorsal surface of the 
vomers and palato-pterygoids. 
Along the lateral borders of the dorsal surface are two articular 
surfaces on which rest the cartilaginous rods of the chondrocranium 
which form the sides of the brain case. The posterior ends of these 
rods lie in small notches at the antero-lateral angles of the broad 
posterior part of the parabasal. Posterior to these sockets are articular 
surfaces for the otic capsules and on the middle of the posterior border 
of the dorsal surface lies the cartilaginous basi-occipital, connecting 
the otic capsules. 
The upper ja w. — The premaxillary, as in Spelerpes, is a single 
bone, another point in which Typhlomolge differs from the Proteidae. 
In shape it resembles the Greek letter 7 r. The transverse portion is 
dentigerous and extends across the snout, being deeply grooved on 
the posterior surface to encase the broad anterior portion of the 
