— 166 — 



of the liead, lies in a nearly horizontal position directed postero-laterally and but slightly upward. 

 This ridge-like postorbital edge is perforated by a large opening which represents the trigemino- 

 facialis Chamber, and from this Chamber five foramina lead into the cranial cavity. One of these 

 foramina transmits the truncus ciliaris profundi accompanied by the encephalic branch of the jugular 

 vein; a second one transmits the ramus ophthalmicus lateralis; a third the truncus trigeminus and 

 related lateralis nerves, and a fourth the truncus facialis. The fifth foramen certainly transmits 

 the nervus abducens, and probably that nerve alone, the palatinus facialis doubtless traversing the 

 facialis foramen, but these nerves were not traced in the adult. In 5 cm specimens, they both traverse 

 the ventral portion of the facialis foramen, enter the trigemino-facialis Chamber, and traversing 

 that Chamber, issue through its trigeminus opening. The Chamber is also traversed, as usual, by 

 the jugular vein and the truncus sympatheticus. 



Dorsal to the trigemino-facialis Chamber, the tall postorbital edge of the proötic expands 

 abrupt!}^ and bears, on this expanded portion, an elongated and curved articular surface the axis 

 of which is directed dorso-posteriorly while the surface itself is directed laterally. This surface gives 

 sliding articulation to a curved surface on the anterior one of the four articular heads of the hyoman- 

 dibular. Slightly dorsal (here lateral) to this articular surface the bone is connected by synchondrosis 

 with the sphenotic. 



The orbital portion of the proötic is large, is transverse and nearly vertical in position, inclining 

 upward and slightly forward, and arises from the internal surface of the lateral portion of the bone 

 slightly posterior to its anterior edge. Near its dorsal edge it is perforated by the oculomotorius 

 foramen. Its mesial edge does not reach the middle line, a small ventral portion of the edge suturating 

 with the transverse ridge on the dorsal surface of the parasphenoid, while the dorsal portion of the 

 edge is free and lorms part of the boundary of the pituitary opening. The lateral portion of the bone 

 has its ventro-mesial edge bevelled on its outer surface, and there suturates with the lateral edge 

 of the parasphenoid. Internal to this line of sutural contact, and posterior to the orbital portion of 

 the bone, the edge of the proötic is slightly grooved and this groove lodges the lateral edge of a broad 

 band of cartilage which extends across the middle line to the corresponding edge of the proötic of the 

 opposite side. The hind edge of the band is lodged in a groove on the anterior edge of the basioccipital, 

 its anterior edge reaching to the posterior surface of the transverse ridge on the dorsal surface of the 

 parasphenoid. This anterior edge of the cartilage seems not to be a free edge, but to rather abruptly 

 but insensibly pass into a delicate membrane which is connected, anteriorly, with the stouter mem- 

 brane that fills the pituitary opening of the brain case. Two suppositions are accordingly possible 

 to explain the conditions here; either the postpituitary portion of the proötic bridge has been depressed 

 and appressed upon the underlying ventral flanges of the proötics, as assumed by Gill ('91a, p. 379) 

 in bis descriptions of Hemitripterus, or the entire proötic bridge has been shortened and shoved 

 forward nearly to the anterior edges of the ventral flanges of the proötics and there tilted upward 

 to form, on either side, the orbital portion of the corresponding bone. The conditions found in 

 Blennius, to be later described, indicate that the first of these two assumptions is probably the proper 

 one, but they also indicate that the process has not been simply one of depression and appression 

 of the proötic bridge, but also one of reduction of the ventral flanges of the proötics. These ventral 

 flanges have, apparently, been so greatly reduced that they are practically suppressed, and the 

 primary floor of the cranial cavity is here formed by the proötic bridge alone, that bridge lying 

 directly upon the parasphenoid. The hypophysial fenestra is then represented, in its posterior 



