— 106 — 



tions with these two ganglia that they do in Scorpaena, but they here both lie along the external 

 surface of the proötic. 



There is thus, in Cottus, no bony trigemino-facialis Chamber, the outer wall of that Chamber 

 being represented by membrane only, as it is in the 44 mm and 55 mm specimens of Scorpaena. But 

 singularly enough, the outer wall of the internal jugular canal, which canal is simply an anterior 

 Prolongation of the trigemino-facialis chamber, has been ossified in Cottus, while in Scorpaena it 

 is almost wholly membranous. In the specimen of Cottus used for the figure, two little eminences 

 on the outer surface of the proötic indicate a partial ossification of the outer wall of the trigemino- 

 facialis Chamber. In the other two of my three specimens these eminences did not exist, the bone 

 there being simply slightly hollowed where the trigemino-facialis foramina perforated it. 



The proötic of Cottus has a perfectly normal mesial process, connected, by intervening car- 

 tilage, with its fellow of the opposite side. The prepituitary portion of the process is short, not reaching 

 the middle line. The pituitary opening is thus not closed anteriorly by bone, and so forms an apparent 

 part of the large orbital opening of the brain case. The membrane that closes the latter opening 

 is greatly thickened in the optic and basisphenoid regions, and there becomes a thick, tough, fibrous 

 structure the lateral edges of which are attached to both edges of the internal jugular recess. The 

 nervus oculomotorius pierces this membrane, on either side, near its lateral edge and enters the myo- 

 dome, lying, in this part of its course, between the ascending process of the parasphenoid and the 

 basisphenoid membrane, and hence morphologically between the two legs of the alisphenoid; its 

 normal position. A median, encephalic artery, formed by the union of the internal carotids of opposite 

 sides, pierces the membrane near the anterior edge of the membranous jjituitary fossa, and enters 

 the cranial cavity. 



The MYODOME is well developed; and it would seem as if the skull of this fish must have 

 been unknown to Cope when he placed the Cottidae among those fishes in which the canal is wanting. 

 The hind end of the canal is continued a short distance in the basioccipital, but it does not open 

 posteriorly on the outer surface of the skull. 



The PTEROTIC presents no features differing especially from those of the bone in Scorpaena, 

 excepting that it lodges two sense organs of the main infraorbital line, one innervated by the ramus 

 oticus and the other by the supratemporal brauch of the nervus lineae lateralis vagi; the preoperc- 

 ular canal joining the main infraorbital between these two organs. The bone accordingly contains 

 a post-preopercular latero-sensory ossicle, this ossicle not being found in either Scorpaena or 

 Sebastes. 



The BASIOCCIPITAL is much less deeply and extensively grooved by the posterior portion 

 of the myodome than in Scorpaena, and the cavum sinus imparis is simply a shallow depression. 

 The bone forms part of the boundary of the foramen magnum, as in Scorpaena, and otherwise 

 resembles the bone in that fish. 



The EXOCCIPITAL is perforated by three foramina, as in Scorpaena, but the occipital 

 foramen is very small and represents a part only of the foramen of Scorpaena; a deep incisure in 

 the hind end of the exoccipital, immediately dorsal to the base of its condylar process, transmitting 

 the larger part of the nerves that traverse the occipital foramen in Scorpaena. The bone, as in Scor- 

 paena, has a mesial process, which rests on the dorsal surface of the basioccipital and roofs the hind 

 end of the saccular groove. 



