— 207 — 



13. The alisphenoid is perforated, in Scorpaena, Trigla and Lepidotrigla, by a foramen which 

 transmits delicate branches of the external carotid arterv and the vessel x, these branches being 

 accompanied by a nerve which is composed of the lateralis fibers destined to innervate the terminal 

 organ of the supraorbital canal and of certain other general cutaneous or communis fibers. In Dactylo- 

 pterus, the nerve that traverses the foramen does not contain lateralis fibers; the nerve destined to 

 supply the terminal organ of the supraorbital canal there having an extracranial course. The ali- 

 sphenoid is also perforated, or notched, in Scorpaena, Trigla and Lepidotrigla by another foramen, 

 which transmits the homologue of the anterior cerebral vein of my descriptions of Amia. These 

 foramina, one or both, are found in the other mail-cheeked fishes also, but the arteries and veins 

 that traverse thera were not there traced. 



14. The parietal is fused, in all the mail-cheeked fishes examined, with a mesial extra- 

 scapular latero-sensory element to form a single bone, which I have called the parieto-extra- 

 scapular. This same fusion of these two bones is also found in the Characinidae and Cyprinidae 

 (Allis '04) and has been definitely established in no other fishes that I know of, excepting Chanos. 



15. The side walls and floor of the skull of osseous fishes are more or less completely double 

 in the sphenoid (orbito-temporal, Gaupp) and labyrinth regions; these walls being there represented 

 m varying proportions by membrane, cartilage or bone. Between the two walls, in the sphenoid 

 region, lies the mvodome with its upper lateral or trigemino-facialis Chambers, while between the two 

 walls in the labyrinth region lie the membranous ears. The myodome and its trigemino-facialis 

 Chambers are thus all intramural Spaces. The floor of the myodome proper is perforated by the 

 hypophysial fenestra, while its roof is perforated by the pituitary opening. These two perforations 

 of the cranial floor are doubtless strictly homologous in all vertebrates, but it must be determined, 

 in each case, which one of the two perforations is in cjuestion. The myodome proper lodges a cross- 

 commissure of the pituitary veins, and is the probable homologue of the cavernous and intercavernous 

 sinuses of the human skull. The postpituitary portion of its roof apparently always chondrifies, 

 and is the postclinoid wall. The prepituitary portion of its roof does not usually chondrify (Argyro- 

 pelecus may be an exception), and it and the basisphenoid, one or both, represent the anterior clinoid 

 wall. The orbital opening of the myodome, on either side, is the sphenoidal fissure. 



The trigemino-facialis chamber of either side is, in the mail-cheeked fishes, and probably 

 in most other teleosts, separated from the myodome by a partition of bone. It lodges the trigeminus 

 and related sympathetic ganglia, and is the homologue of the cavum Meckelii of the human skull. 

 Its outer wall is, in all the mail-cheeked fishes examined, excepting Cottus, represented by a narrow 

 bridge of bone, this wall of the chamber here forming the outer surface of the skull. In Cottus this 

 outer wall is entirely of membrane, the inner wall of the chamber thus here forming the outer surface 

 of the prepared skull. The internal wall of the chamber forms part of the bounding walls of a recess 

 on the internal surface of the skull, and this recess lodges the lateralis and communis portions of the 

 V — VII ganglionic complex. In Amia these portions of the ganglionic complex lie in the upper lateral 

 Chamber of the myodome. There is accordingly question as to whether the inner wall of the chamber 

 of teleosts corresponds exactly to the same wall in Amia. In any event, the recess that lodges, in 

 teleosts, the lateralis and communis ganglia would seem to be the homologue of some part of the 

 aqueduct of Fallopius. 



The trigemino-facialis chamber is continued anteriorly by an intramural space that lodges the 

 jugular vein and the truncus ciliaris profundi. The outer wall of this space is largely of membrane in 



