384 The Ohio Naturalist. [Vol. Ill, No. 5, 



of a basi-branchial plate, (d) the large size and peculiar contour 

 of the urohyal, (c) the ceratohyals, which hang free from the 

 basihyal, and do not articulate with the quadrate as they do in Rana 

 and Cryptobranchus, and (//) the absence of any "free" branchials, 

 that is, any branchials unattached to the basihyal cartilage. 



Basihyal. — (Plates 8, 9, bh. ) The basihyal is a rounded and 

 slender rod of cartilage projecting well forward into the tongue 

 and prolonged posteriorly into the slender urohyal. Just behind 

 the rounded anterior extremity is found the articulation of the 

 ceratohyals. This articulation is not close, but the ceratohyals 

 seem to be rather loosely swung from the front of the basal cart- 

 ilages. From the posterior portion of the cartilage, the first and 

 second cerato-branchials are given off in close succession, and 

 from this point the cartilage continues as the urohyal. In the 

 specimen prepared, the basihyal and branchial cartilages were 

 probably somewhat distorted, on account of the unnatural posi- 

 tion of the tongue, so that in the drawing (Plate 8) they are 

 higher in relation to the rest of the skull than they should be ; 

 the measurements, however, and relative sizes are accurate. 



Urohyal. — (Plate 9, uh. j The urohyal bar is much longer 

 in Spelerpes longicaudus than in the same stage of the frog. It 

 is median and basal, and forms simply an elongation of the 

 basihyal. The urohyal terminates, however, in a flattened spatula, 

 which affords a place of insertion for two heavy muscles. 



Ceratohyals. — (Plates 8, 9, ch.) The ceratohyals are a pair 

 of curving bars of cartilage, swinging freely from a loose articu- 

 lation with the anterior part of the basihyal. Their direction is 

 dorso-caudal, and they terminate freely in the mesoderm a short 

 distance behind the quadrate and external to the auditory capsule. 



Branchial Arches. — (Plate 9.) The branchial cartilages at 

 the given stage of this specimen are all in junction ; that is, none 

 of them hang free at either extremity. They maj' be classified 

 into three pairs of ceratobrauchials and four pairs of epibranchials. 



The first ceratobranchial is the largest of all the branchial bars 

 (Plate 9, bra.). It is given off from the anterior extremity of 

 the basihyal. It curves slightly down and out and shortly gives 

 rise to the first epibranchial and joins with the second cerato- 

 branchial in originating the second epibranchial arch. The sec- 

 ond ceratobrauchials (Plate 9, brb.) are at their beginning notice- 

 ably smaller than the first ceratobrauchials, but soon increase in 

 size. This ceratobranchial gives rise to the .second epibranchials 

 (in conjunction with the first ceratobranchial bar) and to the 

 third ceratobranchial (Plate 9, brc). The third ceratobranchial 

 soon divides into the third and fourth epibranchial cartilages 

 (Plate 9, be, bd.). The four epibranchials run free for some 

 distance and at their posterior extremity are again united to one- 

 another by a curving bar of cartilage. 



