3 86 
The Ohio Naturalist. 
[Vol. Ill, No. 5 , 
M. masseter, and is inserted on the rounded base of the lower 
mandible (Meckel’s cartilage). Turning now to the ventral sur- 
face, we find the — 
M. Subm axillaris. — (Plate u, Fig. 2, msb.) This muscle 
is a broad, thin sheet of fibres covering in the space between the 
mandibles almost completely. It extends between the two rami 
throughout their extent, save for a small space at their anterior 
extremity. The muscle is a very delicate one, and the fibres are 
loosely conjoined, seeming to indicate a tardy development as 
compared with the other muscles. The function of the submax- 
illaris is still a matter of doubt, but that it is closely connected 
with the respiratory function seems fairly certain. 
M. SubmenTALIS. — (Plate n, Fig. 2, msm.). This small aud 
insignificant muscle appears as a tendinous band at the extreme 
anterior portion of lower jaw. Its function is to approximate the 
rami of the jaw, but it appears to be of small practical consequence. 
MUSCLES OF THE BRANCHIAL APPARATUS. 
The branchial muscles of the 12 mm. Spelerpes longicaudus 
show a very marked similarity to those of the adult Crypto- 
branchus, although they are not quite so numerous, or so com- 
plex. The group consists of a paired sternohyoid, a hypobrancliial, 
a constrictor, levator and depressor of the arches, a geniohyoid, a 
well-defined cerato-branchialis and a small omohyoideus. 
M. Sterno-hyoideus. — (Plate n, Figs. 2, 3, msh.) This 
muscle is a direct continuation of the fibres of M. rectus abdominis. 
The recti abdomini, as they pass forward from the posterior part 
of the body, alter both in contour and in position. In the body 
proper, the}' are seen as two thin vertical sheets of muscle, bound- 
ing the body cavity. As they pass into the head region, how- 
ever, they gradually assume a median position and become thick- 
ened to form a pair of round, heavy muscles, which fuse in the 
region of M. temporalis, aud have their common insertion on the 
basihyal at the point of union of the first ceratobranchial. The 
muscle is superimposed on the urohyal cartilage. 
M. Geniohyoideus. — (Plate 11, Figs. 2, 3, mgh.) This 
muscle arises on the lower mandible, just posterior to the inser- 
tion of M. submen tails. From this point it extends directly 
backward, as a small rope-like muscle, to its insertion on the 
spatular end plate of the urohyal cartilage. Its function is to 
draw the branchial apparatus forward. 
M. Hypobranchialis. — (Plate 11, Fig. 3, mhb. ) This muscle 
arises 011 the ventral surface of the ceratohyal cartilage, inside of 
the origin of the following muscle. Its fibres run posteriorly and 
obliquely inward, and are inserted along the course of the posterior 
two-thirds of the first epibranchial, except at the posterior end of 
the branchial. 
M. Ceratobranchialis. — (Plate 11, Fig. 3, mcb.) This 
muscle is a thin sheet of fibres arising on the ventral surface of 
