128 BULLETIN OF THE ESSEX INSTITUTE. 



hardly be admitted to exist. The great similarity pointed 

 out above between the skulls of Polypterus and the trout 

 and the many points in which they differ from the typical 

 skull of the Batrachia cause me to feel considerable hesi- 

 tancy about accepting the theory of the Crossopterygian 

 ancestry of the Batrachia. But, while the presence in 

 Polypterus of a large hyomandibular cartilage, a quadrate 

 well removed from the otic capsule and a strong supraor- 

 bital band, as well as the absence of any fenestra ovalis 

 or stapes, will remain important obstacles to this view 

 until transitional stages are found, perhaps these difficul- 

 ties are less than those attending the Dipnoan theory. 

 Attention may also be called to the fact that in Polypterus 

 there is a limited median capsular wall, which is not found 

 in either the trout or Protopterus but which regularly 

 occurs in the Batrachia. 



Protopterus annectens (Figs. 30-32). 



A model of the chondrocranium of Protopterus gives 

 us a basis from which to compare the Dipnoi on the one 

 hand with the Batrachia, to which they have been consid- 

 ered to be closely related, and on the other to the 

 Teleosts and Ganoids. 



Viewed as a whole the massive character of many of 

 the cartilages of this skull is a most striking feature. 

 Ossification in the occipital region somewhat obscures the 

 relations between the skull and the first vertebra. The 

 occipital processes are fused with the otic capsules leaving 

 large jugular foramina in the usual position. The remnant 

 of the notochord is imbedded in a solid parachordal plate 

 extending from the posterior end of the skull forward to 

 the middle of the otic region. On each side of the me- 

 dian line at the anterior end of the parachordal plate is an 



