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cranial cavity through the foramen VII of Bridge's figure 6, the 

 external carotid and jugular vein continuing onward in the canal and 

 issuing on the outer surface of the skull through the anterior opening 

 of the canal, this anterior opening undoubtedly being the foramen 

 marked V" in Bridge's figure 2, VII in his figure 3, and VII' in his 

 figure 4. 



Having reached the outer surface of the skull, through the anterior 

 opening of the facialis canal, the external carotid runs forward with 

 the jugular vein and, in the one specimen in which the details of the 

 distribution of the artery were traced, soon gives off two small branches, 

 arising close together. One of these branches separates into two parts, 

 one of which pierces the cranial wall by a small and independent 

 foramen to enter the cranial cavity, while the other runs downward 

 and backward, sends a branch to the protractor hyomandibularis muscle, 

 and then is distributed to tissues in the region of the pseudobranch. 

 The other branch turns upward, and after also sending a branch to 

 the protractor hyomandibularis traverses the oticus facialis canal and 

 is distributed to tissues in the f-shaped groove on the dorsal surface 

 of the skull. These two small branches of the external carotid are 

 thus both related to the spiracular canal. Slightly anterior to them, 

 another small branch is sent into the cranial cavity, by an independent 

 foramen, and then a fourth small branch is sent downward and back- 

 ward internal to the protractor hyomandibularis, supplying that muscle 

 and tissues of the region. Immediately anterior to this fourth branch 

 the external carotid separates into two terminal portions, which may 

 be called the orbito- nasal and maxillo - mandibularis arteries, this 

 separation taking place just as the artery reaches the hind edge of 

 a large foramen that must be the foramen V of Bridge's figure 3. 



The orbito-nasal branch of the carotid, running forward, soon 

 gives off an ophthalmic branch which runs forward dorsal to the nervus 

 opticus, accompanying the ophthalmicus superficialis nerve and reaching, 

 with that nerve, the dorsal surface of the skull. A second branch is 

 then soon given off which also runs forward dorsal to the nervus 

 opticus, sending branches to certain of the eye-muscles and then 

 entering the nasal cavity. The remainder of the nerve, after giving 

 off" these two branches, runs forward in the orbit ventral to the nervus 

 opticus, sends branches to certain of the eye-muscles and then leaves 

 the orbit to reach the snout of the fish. The orbito-nasal artery of 

 Polyodon would thus seem to represent, approximately, the orbito- 

 nasal and facialis-maxillaris arteries, together, of Allen's descriptions 

 of the Loricati; but' the orbito-nasal artery of those descriptions is a 

 branch of the internal instead of the external carotid. 



