EXTINCT BATRAOHIA. 



363 



fluent with the corresponding superior element, and the first is similarly- 

 confluent, or, as Fischer interprets it, the first branchihyal of the supe- 

 rior series extends to the axialhyal (fig. 7, h'). In Muraonopsis a greater 

 divergence from the archetype exists. With all the peculiarities of Pro- 

 tonopsis, it further almost loses the second hsemal element, bv", which ap- 

 pears at maturity as a process on the first pleural element. 



Fig. 8. 



PKOTONOrSIS HORUIDA. 



These characters may be tabulated as follows : 



A Third haemal branchihyal present. 



X First and second hsemal branchihyals free and distinct Cocyiinus. 



XX First and second haemals separate from each other, but confluent with 



their pleural elements Protonopsis. 



Amphiuma. 

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



AA Third haemal element wanting. 

 X Second heemal element reaching the axis Siren. 



(Amblystoma, 

 Triton, 

 Salamandra. 

 XX Second hajmal element reduced, not reaching axis Proteus. 



Now, it has been pointed out that Cocytinus agrees with the last named 

 genera in the large development of the first pleural and haemal branch- 

 ihyals, 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 those genera, and the third is larger and supports the fourth as well 

 as its own pleural element. (Fig. 4, bv", bv'".') 



