27(3 



SLTPPLPJMENT TO TllP] EXTmCT BATRACHIA 



COCYTINUS, Gope. _ , - , . ' 



Proceed. Amer. Philos. Soc, 1871, p. 177. 



Vertebrae and ribs osseous ; anterior limbs, thoracic shields and abdominal arma- 

 ture apparently wanting. Teeth on the premaxillary bone, none on the maxillary, 

 llyoid elements largely developed. An axial hyal with basihyal on each side, closely 

 united with the corresponding ceratohyal, at the end of which is an element in the 

 position of a stylohyal. Iltemal or basal branchihyals three, the anterior two each 

 supporting one pleural branchihyal, and the third supporting one also. The first or 

 anterior hjemal branchihyal on the inner side of the ceratohyal, approaching the 

 median line, and with elongate pleural element. Urohyal not seen. 



Such are the characters of a genus, whose affinities are interesting but somewhat 

 obscure. The hyoid apparatus is better developed than in any other here described, 

 but it is by no means certain that it was brahchiferous at maturity, nor does this 

 character on the other hand render it certain that the animal is the larva of one of the 

 other forms here described. The well ossified ribs and vertebrae are favorable, 

 though not conclusive evidence for adult age, while the structure of the hyoid appa- 

 ratus is moi"e like that of the gilless genera ^w?j^9/iM(m« and Pro 'o?iOj;-szs, than it is 

 like the branchiferous genera Siren and Necturus^ or the branchiate young of Sala- 

 manders. Thus it differs from Proteus iu the presence of the first axial hyal and the 

 two first basihyals, from this genus and Necturus in the possession of four distinct 

 pleural branchihyals. In this it agrees with Ampliiama, as it does also with I*ro o- 

 nojjsis, in the three hsemal branchihyals.'^' Siren has only two of these elements, the 

 first and second witliout the third. As a consequence in Siren the third and fourth 

 pleural elements have no corresponding haemal support, an arrangement totally ditterent 

 from that of Cocyt'mus. The arrangement in larval Amhlystoma and Triton is quite 

 similar to that in Siren, excepting that in Triton, the small basihyals are present. 



The question as to whether this genus was in life branchiferous or not, is not 

 easily decided, since the hyoid apparatus is about equally developed in the branchi- 

 ferous genera Siren and N^turus, and the air breathers Amphiuma and Protonopsis. 

 Some considerations however point to an air breathing type, like the last two, though 

 the individual may possibly have been immature. In the gill-bearing genera, as well 

 as in the larva? of Amblystoiiuje, Tritons, etc., the branchial arches approach nearest 

 to archetypical ])crfection. Thus in the Sireii lacertina, two of the four superior 

 branchihals are supported by corresponding inferior or hsemal branchihyals, and these 

 in turn are articulated each to its proper axial hyal. The absent elements are the two 



*For the noineuclature of these bones, I follow Fischer's Uebei die Peiennibi-anchiateu und Derotremeii : 

 Hamburg, 1804. 



