— 123 — 



tube of the supraorbital canal. Tliis nerve, as in Scorpaena, perforates the alisphenoid, then runs 

 upward along the inner wall of the skull, traverses the lateral fontanelle, and, perforating the frontal, 

 reaches its organ. As in Scorpaena, the nerve is accompanied, as it traverses its foramen, by branches 

 of the external carotid artery and the vessel x. 



On the external surface of the bone, near its ventral edge, there is a short and slight ridge which 

 is continued downward onto the external, ventro-anterior surface of the mesial process of the proötic. 

 Towarcl this ridge a small process projects dorsally from that part of the proötic that fornis the anterior 

 edge of the lateral surface of the brain case, this process being of very variable length, and the process 

 and the ridge above it being connected by fibrous tissues. That part of the ridge that lies on the 

 alisphenoid represents a slight remnant of the parasphenoid leg of that bone, the part that lies on the 

 proötic here replacing a part of that process of the parasphenoid that, in Cottus, comes into contact 

 with the alisphenoid. 



On the internal surface of the alisphenoid, at about its antero-dorsal quarter, there is a brace- 

 like thickeuing of the bone, which is the greatly developed homologue of the sniall ridge described 

 on the internal surface of the alisphenoid of Scorpaena. The flat dorsal surface of the brace is carti- 

 laginous in places, reaches the level of the dorsal edge of the bone, and abuts against the ventral 

 surface of the frontal ; the bind edge of this surface of the brace almost reaching the anterior edge of 

 the supraoccipital. The lateral edge of the dorsal surface of the brace forms the mesial boundary of 

 the anterior half of the lateral cranial fontanelle, its mesial edge being in synchondrosis with a large, 

 median postepiphysial interspace of cartilage which extends forward from the anterior edge of the 

 supraoccipital. The anterior edge of this postepiphysial interspace of cartilage is slightly concave, and 

 extends from the anterior edge of the alisphenoid of one side to that of the other side. From the 

 antero-lateral corner of the cartilage, a band of cartilage runs postero-laterally along the dorsal edge 

 of the plate-like body of the alisphenoid, the postero-lateral end of the band being continuous with a 

 band of cartilage that runs backward along the mesial edges of the sphenotic and pterotic and forms 

 the lateral boundary of the lateral cranial fontanelle. In Trigla gurnardus, a specimen of which was 

 used for the figure showing a dorsal view of the chondrocranium, there was a deep bay in the anterior 

 edge of the postepiphysial cartilage, much larger and deeper than that found in the specimens of 

 Trigla hirundo that were examined. 



The BASISPHEXOID has a long pedicle which is directed downward and forward at an angle 

 of from 30" to 45°, the two wings of the body of the bone being directed laterallyand slightly upward. 

 The bone does not come into bounding contact with the alisphenoid. Along the dorsal surface of the 

 body of the bone, on either side, the optic nerve pierces the membrane that closes the orbital opening 

 of the brain case and enters the orbit. Slightly dorsal to the optic nerve, the nervus olfactorius pierces 

 the same membrane, and from there runs forward along the lateral surface of the interorbital septum, 

 lying wholly free in the orbit. In the bind edge of the body of the bone, in my largest specimen, there 

 is a median and iraperfectly closed foramen which unquestionably transmits the median encephalic 

 artery formed by the fusion of the internal carotid arteries of opposite sides of the head. 



The LATERAL SURFACE OF THE BRAIN CASE is relatively flat and narrow, and its 

 anterior edge has a pronounced reentrant angle, at about the niiddle of its height. That part of this 

 edge that lies ventral to tlie point of the angle inclines forward and downward and is formed by a thin 

 plate of bone which, in its dorsal portion, projects forward considerably beyond the adjoining portion 



