386 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. SuBMAXiLLARis.— (Plate II, 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 II, Fig. 2, m.sm.). This small and 

 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 hypobranchial, 

 a constrictor, levator and depressor of the arches, a geniohyoid, a 

 well-defined cerato-branchialis and a small omoh^-oideus. 



M. Sterno-hyoideus. — (Plate 11, Figs. 2, 3, msh. j This 

 mu.scle 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, they are seen as two thin vertical sheets of muscle, bound- 

 ing the body cavit}'. 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, and have their common insertion on the 

 basihj-al 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. submentalis. From this point it extends directh* 

 backward, as a small rope-like mu.scle, to its insertion on the 

 .spatular end plate of the urohyal cartilage. Its function is to 

 draw the branchial apparatus forward. 



M. Hypobranchialis. — ( Plate 1 1 , Fig. 3, mhb. ) This muscle 

 arises on the ventral surface of the ceratoh3'al cartilage, inside of 

 the origin of the following muscle. Its fibres run posteriori}' 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 

 mu.scle is a thin .sheet of fibres arising on the ventral surface of 



