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two arteries. In Lepidosteus, it is the main efferent pseudobranchial artery, itself, that here unites 

 with the internal carotid, traversing, to reach that artery, the imperfeetly closed foramen in the 

 anterior edge of the ascending process of the parasphenoid. This difference in this artery, in these 

 two fishes, is doubtless due to the absence of a choroid gland in Lepidosteus; that orbital continuation 

 of the artery that supplies that gland in Amia naturally being suppressed with the gland, in Lepi- 

 dosteus, and the comniunicating branch of Amia becoming, in Lepidosteus, the direct anterior continua- 

 tion of the main artery. 



The palatinus facialis and external carotid of Lepidosteus run upward and backward, as 

 already stated, in a groove that leads into a trigemino-facialis chamber in the proötic. This chamber 

 has a very large trigeminus, and a smaller facialis opening, and its bony mesial wall is a direct posterior 

 continuation of the bony wall that encloses the anterior part of the cranial cavity; Lepidosteus, in 

 this, resembling Scomber and the mail-cheeked fishes, and differing markedly from Amia. The mesial 

 wall of tbe chamber is perforated by a single large foramen for the roots of the trigemino-facialis 

 nerves, two small processes representing the beginnings of a Separation of the foramen into two or more 

 parts. Slightly antero-ventral to this foramen the anterior edge. of the proötic is perforated by another 

 foramen, the anterior border of which is formed by a small flat bar of cartilage which, rising from 

 the trabecular cartilage and extending upward to the ventral edge of the aüsphenoid, separates the 

 foramen from the ventral portion of the optic fenestpa. This foramen transmits the pituitary vein, 

 which vein arises beneath the hypophysis, in direct communication with its fellow of the opposite 

 side, and from there runs dorso-antero-laterally to traverse its foramen and fall into the (internal ?) 

 jugular slightly posterior to the point where that vein is joined by the orbito-nasal vein. The pitui- 

 tary vein receives a small branch, on either side, from the cross-canal of Sagemehl's descriptions, 

 these branches being traced in sections and not in the adult. The vein, in the adult, lies, in its intra- 

 cranial course, beneath a mass of fatty tissue which covers the floor of the cranial cavity, and this 

 fatty tissue in the cranial cavity of the skull of fishes is said by Sagemehl ('84a) to lie between inner and 

 outer limiting membranes which are parts of the dura mater. Some part of this tissue, in Lepidosteus, 

 is accordingly the homologue of the tough glistening membrane that, in Amia, forms not only the roof 

 of the anterior portion of the myodome, but also the mesial wall of the trigemino-facialis chamber 

 of that fish. The foramen that transmits the pituitary vein, in Lepidosteus, is thus quite certainly 

 the equivalent of some part of the ventral portion of the orbital opening of the myodome of Amia. 



Immediately dorsal to the foramen for the pituitary vein, between the adjoining edges of the 

 proötic and aüsphenoid, there is another foramen, which transmits the nervus oculomotorius and 

 probably the radix profundi also, for although this latter nerve, in my 80 mm specimen, pierces the 

 cartilaginous cranial wall close to but wholly separate from the oculomotorius, I do not find a separate 

 foramen in the one adult skull that I have examined in this connection. Van Wijhe ('82) says that 

 he found the profundus issuing by a separate and independent foramen. Somewhat dorsal to these 

 two foramina, in the sections of my 80 mm specimen, the trochlearis pierces the cranial wall, and, 

 slightly posterior to that nerve, the wall is perforated by a branch of the orbito-nasal vein. These 

 two latter foramina are, one or both, represented, in my adult specimen, in a short canal that tra- 

 verses the aüsphenoid slightly dorsal to the oculomotorius foramen. 



Stannius ('49, p. 19) says that, according to Müller, the oculomotorius, trochlearis and trige- 

 minus of Lepidosteus all issue through a single large foramen in the ,, Keilbeinflügel"; a statement 

 that is certainly not wholly correct. 



