— 103 — 



Position, and, on one side of one of my three specimens, it almost entirely closed not only the 

 posterior but also the lateral opening of the temporal fossa, leaving only small openings on either 

 side of it. On the other side of that one specimen, and on both sides of the two other specimens, the 

 opening lateral to the process was the larger of the two, the opening mesial to the process being practic- 

 ally closed in one of the two specimens. Mesial to the base of the opisthotic process there is, on the 

 under surface of the bone, an articiilar facet, and directly posterior to the base of the process there 

 is an articular eminence; the two surfaces giving articulation to the supraclavicular. The body of 

 the bone is traversed by the main infraorbital canal and lodges one organ of that canal, inner- 

 vated by a branch of the supratemporal branch of the nervus lineae lateralis. The bone is 

 without spine. 



The SUPRACLAVICULAR has, on the anterior corner of its dorsal edge, a facet which gives 

 articulation to the articular eminence on the under surface of the suprascapular. From the mesial 

 surface of this part of the bone a process arises, directed antero-mesially, and on its anterior end 

 it has an articular eminence which articulates with the articular facet on the suprascapular. The 

 dorsal edge of the bone is traversed by a short section of the main infraorbital latero-sensory canal 

 and lodges one organ of that line. The posterior corner of the bone is prolonged into the stout supra- 

 clavicular spine. 



The PARASPHEXOID has, on either side, a tall and broad ascending process with two dorsal 

 ends. These two dorsal ends are pointed and separated by a large V-shaped incisure in my small 

 specimens, but bifid and separated by a shallow depression in the large specimen used for illustration. 

 The posterior and shorter end, or point is directed toward, and nearly reaches the trigeminus foramen, 

 and is in contaet with and firmly bound to the proötic. The anterior and longer point is in contact 

 with and firmly bound to the alisphenoid, and almost, if not quite reaches in certain specimens the 

 ventral edge of the ventral flange of the frontal. These two ends, or points, belong respectively to 

 posterior and anterior portions of the ascending process, and between the two portions the outer 

 surface of the process is quite concave, its inner surface being correspondingly convex. Between 

 the posterior portion of the process and the body of the parasphenoid there is a normal internal 

 carotid foramen. 



On the dorsal surface of the parasphenoid, between the bases of the ascending processes, there 

 is a raised median portion on the dorsal surface of which there is a relatively large median pit, the 

 point of the pit directed downward and backward. The pit gives Insertion to the recti interni muscles. 

 Immediately posterior to it there is a depressed region on the dorsal surface of the bone, and then a 

 raised median rib, this rib lying between the ventral edges of the proötics of opposite sides and 

 forming the median portion of the floor of the myodome. 



The ALISPHE.XOID is bounded posteriorly by the sphenotic and proötic, with both of which 

 bones it is in synchondrosis. Antero-dorsally it is overlapped externally by the ventral flange of the 

 frontal, and ventrally it is in contact with the anterior portion of the ascending process of the para- 

 sphenoid. It has short but broad basisphenoid and parasphenoid legs, these two legs enclosing a 

 V-shaped groove which begins at nothing, at the anterior end of the ventral edge of the bone, and 

 deepens gradually toward its bind end. The external bounding plate of this V-shaped groove is the 

 parasphenoid leg of the bone and is the part of the bone that is in contact with the ascending process 

 of the parasphenoid. The internal bounding plate of the groove is the basisphenoid leg of the bone, 



