THE CHONUKOCRANIUM IN THE ICHTHYOPSIIM. 129 



elongate fontanelle (Fig. 32,/). The walls of the otic cap- 

 sules are continuous ventrally with the parachordal plate 

 and dorsally with a strong synotic tectum. From the ex- 

 ternal margin of the otic capsule a broad ledge of cartilage 

 projects horizontally outward, widening as it passes from 

 behind forward where it terminates abruptly. There is 

 no median capsular wall. 



Band-like trabeculse extend forward along the sides of 

 the brain from the dorsal anterior end of the otic capsules 

 to the optic region where they bend around ventrally to 

 form a large ethmoid plate. From the dorsal margin of the 

 anterior end of each trabecula a peculiarly bent antorbital 

 process (^anp) arises. It projects forward and outward, 

 coming into close proximity to, but not fusing with the 

 posterior end of the nasal capsule, and then it bends back- 

 ward, running along the margin of the upper lip. The 

 ethmoid plate narrows down in passing from behind for- 

 ward, and terminates in two processes which bend sharply 

 upward and fuse with the posterior end of the nasal 

 septum. Between these two terminal processes there is 

 an oval fontanelle. 



The nasal capsule is a very peculiar one. The septum 

 is a thin dorsal plate behind, l)ut in front it becomes a 

 solid cylindrical mass of cartilage projecting ventrally 

 between the olfactory organs. The transition from one 

 condition to the oti)er is very abrupt. In front the septum 

 ends in two short laterally directed processes. Six bands 

 of cartilage extend outward and downward from the me- 

 dian septum to a curved marginal band (?«r). Between 

 these bands five apertures of various shapes and sizes are 

 enclosed. The anterior of the six transverse bands pro- 

 jects somewhat beyond its point of fusion with the mar- 

 ginal band. As is seen in the ventral view (Fiii;. 32) a 

 curved process extends inward and upward from the inner 



ESSEX INST. BULLETIN, VOL. XXVIII 9 



