AND KliPTir.IA OF NOliTII AMEKICA. 



277 



axial and two hjemal elements which exist as supports of the posterior two inferioi- 

 brachihyals in the fishes. In the branchiferous Necturus maculatus a considerable 

 modification ensues. The four superior branchihyals are present, but according to 

 Fischer, the first and second haemal elements are confluent. A third inferior branchi- 

 hyal is added. If we now turn to the air-breather Protonopsis liorrida, we observe 

 a marked peculiarity. The third haemal branchihyal remains, while the second is 

 confluent with the corresponding superior element, and the first is similarly confluent 

 or, as Fischer interprets it, the first branchiyal of the superior series extends to the 

 axialhyal. In Muroenopsis (Amjjhiuvna), a greater divergence from the archetype 

 exists. With all the peculiarities of Protonopsis it further almost loses the second 

 haemal element, which appears at maturity as a process on the first pleural element. 



These characters may be tubulated as follows : 

 A Third haemal branchihyal present. 



a First and second haemal branchihyals free and distinct. 



COCYTINUS. 



aa First and second haemals separate fi'om each other but confluent with their 

 pleural elements. 



PKOTONOPSIS. 

 AMPHIUMA. 



aaa First and second distinct from pleurals, but united with each other. 



NECTURUS. 



AA Third haemal element wanting. 



X Second haemal element reaching the axis. 



SIREN, 

 r AMBLYSTOMA. 



Larvae, I triton. 



( SAJLAMANDRA. 



XX Second haemal element reduced, not reaching axis. 



PROTEUS. 



!N^ow it has been pointed out that Cocytinus agrees with the air-breathing genera 

 in the larger development of the first ^i)leural and haemal branchihyals, and that it 

 agrees with them both in the presence of the second and third haemal elements. But 

 these are more distinct than in either of these genei-a, and the third is larger, and 

 siippoi'ts the fourth as well as its own pleural element. 



The presence of the maxillary bone furthermore excludes this genus from near 

 affinity to either the Trachystomata and Proteida, and allies it to the Aiupliiuina and 



A. V. s. — VOU. XV. 



