THE CHONDKOCRANIUM IN THE ICHTHYOPSIDA. 131 



more dorsal of the two is tniversed by two nerves, the 

 ramus lateralis facialis of the seventh (rl) and the ramus 

 ophthalmicus superticialis of the fifth (rs). The more 

 ventral foramen is for a blood vessel (b) . 



Three foramina open upon the ventral surface of the 

 skull in this same region (Fig. 32). Of these the anterior 

 and smallest is for the ramus palatinus superior (I'ps). 

 Tiie other two openings are close together. The more 

 median is for the main trunk of the seventh (v^'^) and the 

 ramus palatinus inferior (lyi). The more lateral open- 

 ing is the ventral end of the foramen for the blood vessel 

 mentioned above. 



The Chondrocranium in the Dipnoi. 



A comparison of the chondrocranium of Protopterus 

 with those of the Batrachia and Fishes at once reveals its 

 unique character. While resembling the typical chondro- 

 cranium of each of these groups in some respects, taken 

 as a whole it is very diflerent from either. The large otic 

 capsule, with thick walls and separate foramen for the 

 ninth nerve, and without a median wall or fenestra ovalis, 

 greatly reseml)les the capsule of Fishes. But the sus- 

 pensorial apparatus is entirely diflerent from that of most 

 Fishes and very similar to that of the Batrachia, that is 

 to say, it is autostylic. According to Huxley ('76) this 

 condition is also found in the Chimasroids and Marsipo- 

 branchii, but in none of the other Fishes. This is un- 

 doubtedly the strongest point of resemblance between the 

 chondrocrania of the Dipnoi and Batrachia. And here 

 the theory of the Dipnoan ancestry of the Batrachia is 

 decidedly at an advantage over the Crossopterygian 

 theory. But this similarity of the otic relations of the 

 quadrate in these two forms is counterbalanced by difler- 



