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that there is no myodome. The list of fishes said, by one author or another, to be without a myodome 

 is thus large, and I have attempted to control it as far as my material and the literature at my disposal 

 will permit. 



In Gadus aeglifinus, Brooks ('84) says that the proötic „unites below with its fellow of the 

 opposite side, and below this with the parasphenoid, the three bones bounding a deep pit, which 

 is open anteriorly, and gives origin to the recti museles of the orbit". This fish would thus seem 

 to possess a myodome, and as another one of the Gadidae, Gadus merlangus, is easily obtained here, 

 I have examined it in this connection. In this fish there is, as in G. aeglifinus, a deep pit opening 

 into the orbit and giving origin to certain of the recti museles. The side walls of this pit are formed 

 by the ventral portions of the proötics, those portions of those bones being capped with cartilage and 

 not meeting in the middle line, a hypophysial fenestra, closed ventrally by the underlying para- 

 sphenoid, thus being left between them. The dorso-posterior wall, or roof of the pit is thick, and 

 is formed by the proötic bridge, that bridge being formed by the mesial processes of the proötics 

 united by a thick median interspace of cartilage. The cerebral surface of this roof slopes postero- 

 ventrallv and forms a convex and triangular-shaped surface between the anterior ends of the large 

 saecular grooves. The wide anterior edge of the roof is bevelled, the bevelled surface sloping antero- 

 ventrally. The transverse edge that lies between this sloping, bevelled surface and the posterior 

 portion of the roof of the pit is continued dorsally, on either side, to form the anterior boundary 

 of the labyrinth recess. The bevelled surface gives attachment to the ventro-posterior edge of a thick 

 tough membrane that fills the large orbital opening of the brain case, a large pocket in this mem- 

 brane, immediately anterior to the proötic bridge, lodging the pituitary body. In the anterior edge 

 of the proötic there is, as in G. aeglifinus, a deep incisure for the exit of the trigemino-facialis nerves, 

 and from this incisure a groove leads ventro-mesially into the anterior end of the myodomic pit. There 

 is no closed foramen whatever in this part of the proötic bone, all of the nerves that pierce the bone 

 in Scorpaena here passing across its anterior edge. There is also no internal carotid foramen between 

 the proötic and parasphenoid, the internal carotid here passing inward across the anterior edge of 

 the expanded, postorbital portion of the parasphenoid; that edge of the parasphenoid lying slightly 

 anterior to the anterior edge of the ventral portion of the proötic. The anterior end of the large 

 saecular groove is separated from the bottom of the trigemino-facialis incisure by only a thin laver 

 of bone. There is no basisphenoid, but there is, as in Cottus, a considerable basisphenoid thickening 

 of the membrane that closes the orbital opening of the brain case. Posterior to this thickened portion 

 of that membrane and partly enclosed in it, in the region of the membranous pituitary fossa, is the 

 transverse commissure of the pituitary veins. There is thus here a normal myodome, but it has been 

 shortened both anteriorly and posteriorly. Posteriorly this shortening is due to a proötic constriction, 

 while anteriorly it is due to the absence of the usual enclosing bones ; for it is evident that the anterior 

 portions of the bodies of the proötics of Scorpaena, and the entire ascending processes of the para- 

 sphenoid of that fish, are absent in Gadus. 



In a prepared skull that I have of Gadus morrhua, the conditions are all similar to those just 

 described for Gadus merlangus, excepting that there is a median ossicle on the cerebral surface of 

 the cartilage of the proötic bridge, not found in G. merlangus. This ossicle is transverse in position 

 and extends from proötic to proötic along the transverse edge that is continuous, on either side, with 

 the anterior wall of the corresponding labyrinth recess. It is a stout ossicle, of perichondrial origin, 

 and has never been described in anv fish so far as I can find. 



