3 82 
The Ohio Naturalist. 
[Vol. Ill, No. 5 . 
is a fully formed capsule. It is possible that the diverse habits 
of the two forms may account for this reversion of development. 
Spelerpes, which spends its larval existence for the most part 
hidden under rocks and in the dark, needs an acuteness of hear- 
ing and a sensitiveness to vibration for which its cousin compen- 
sates by an early developed and well protected eye. 
Trabeculae. — ( Plate io. ) The trabeculae cranii appear as 
two longitudinal bars supporting the anterior end of the brain and 
the nasal sacs. Just behind the superior labial cartilages, they 
are flattened out into a pair of disk-like, slightly concave projec- 
tions serving to support and protect the nasal sacs. There 
is no juncture of the trabecular bars here as is the case in 
the frog. Just behind the nasal capsule, the trabeculae resume 
their rod-like form, presently becoming compressed to form a sort 
of triangle, concave on the outside. This is the optic capsule 
before mentioned. Back of this point, the trabeculae are pierced 
by the optic forameua (Plate 8), and again, still further back, by 
another and larger foramen, which admits some of the larger ves- 
sels to the brain. Just above this latter foramen, the quadrate 
separates from the trabecula. This is given off from the upper 
half of the trabecular bar (Plate 8) and curves down to meet and 
articulate with the lower jaw (Meckel’s cartilage), while the 
lower half curves in to meet its fellow just in front of the noto- 
chord (Plate io, bp.), forming a support for the main part of the 
brain. The auditory capsule is continuous with the quadrate 
above and trabeculae below. From the point of their juncture, 
the trabecular bars continue as a pair of flattened rods — the para- 
ehordals (Plate io), which together with the notochord form the 
floor of the brain case. Just behind the auditory capsule, the 
parachordals show a leaf-like process, which serves as a protective 
case for the medulla and upper cord. 
Upper Labials. — Plates 8, 9, 10, la.) These labials are a 
pair of rounded caps which fit over the ends of the trabeculae. 
They are pointed above and blunt below. It seems that these 
labials should be used, governed by suitable muscles, in sucking, 
in case the larva uses that means of obtaining food, but a diligent 
search failed to reveal any muscles which might be used in that 
way. The superior labials are, like the trabecular cartilages, 
entirely separate from one another. They are so freely and 
loosely articulated, moreover, as to permit of the possibility of 
considerable movement. 
Lower Labials. — (Plates 8, 9, lb.) The inferior labials, on 
the other hand, are so fused as to present the aspect of a single, 
compact cap, which fits over the rounded anterior part of the 
lower jaw. They are comparable in a general way, to the labials 
of Rana. The upper and lower labials are apparently among the 
first cartilages to appear, since at this stage they are very com- 
