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ternal carotid, iu any portion of this part of its course, is separated 

 from the cranial cavity proper by membrane, as described by Ayees, 

 or not, I have not yet determined. Having been joined by the efferent 

 pseudobranchial artery, the internal carotid soon gives off an optic 

 branch and then separates into anterior and posterior cerebral branches, 

 the latter of which fuses posteriorly, in the median line, with its 

 fellow of the opposite side, to form a single median myelonic artery. 

 The optic artery issues from the cranial cavity with the nervus opticus 

 and penetrates the eye-ball with or near that nerve. 



There now remain only the afferent and eiferent pseudobranchial 

 arteries to consider. The afferent artery arises, as Ayers has stated, 

 from the efferent hyoidean artery ventral to the commissure that con- 

 nects the latter artery with the efferent artery of the first branchial 

 arch, the point of origin lying opposite the ventral end of the hyo- 

 mandibular. The artery immediately passes outward between the 

 branchiostegal rays and then upward and forward along the anterior 

 edge of the hyomandibular, between that element and the palato- 

 quadrate, and passing lateral to the spiracular canal reaches the dorsal 

 edge of the pseudobranch (mandibular hemibranch). The efferent 

 pseudobranchial artery arises from the ventral edge of the pseudo- 

 branch. Running forward, internal to the palato - quadrate, it passes 

 ventral to the eye-stalk and then traverses its foramen to enter the 

 cranial cavity, where it falls into the internal carotid artery anterior to 

 the point where that artery anastomoses, in the median line, with its 

 fellow of the opposite side. As it passes under the eye -stalk, the 

 efferent pseudobranchial artery gives off the arteria ophthalmica magna 

 which runs outward and pierces and enters the eye-ball. These two 

 pseudobranchial arteries are thus strictly normal, agreeing in every 

 important respect with those in the Scylliidae and in Mustelus (Allis, 

 1908). According to Ayers' descriptions, the efferent artery falls into 

 the internal carotid posterior to the point where that artery anasto- 

 moses in the median line with its fellow of the opposite side; a con- 

 dition which, as pointed out in my earlier work (Allis, 1908), is ex- 

 ceptional in elasmobranchs. Furthermore, Ayers describes no arteria 

 ophthalmica magna in this fish. 



The arteries in Chlamydoselachus, as above described, are dia- 

 grammatically represented in the accompanying Figure 2, from which 

 it will be seen that they differ in no important particular from those 

 in the Scylliidae and in Mustelus (Allis, 1908), excepting in that the 

 dorsal end of the efferent hyoidean artery has, in Chlamydoselachus, 

 a double connection with the lateral dorsal aorta. The diagram given 



