588 



The secondary, or definitive afferent pseudobranehial artery of 

 Eaja arises from the posterior efferent hyoidean artery, in hne with 

 the intermediate commissures that connect the anterior and posterior 

 efferent arteries in the branchial arteries. Kimning forward, as shown 

 in Hyrtl's figure of Raja clavata, it turns upward and mesially, at 

 nearly a right angle, and enters the pseudobranch, the upward and 

 mesially directed portion of the artery undoubtedly being, as in 

 selachians (Dohrn, 1885), a persisting dorsal portion of the afferent 

 mandibular artery. From the bend in the artery, and from its afferent 

 mandibular portion, branches are sent to the muscles and tissues of 

 the region. 



The efferent pseudobranehial artery arises from the pseudo- 

 branch and having traversed the efferent pseudobranehial canal, 

 already described, falls into the internal carotid artery (lateral dorsal 

 aorta). Immediately before it enters its canal in the chondrocranium 

 it gives off the arteria ophthalmica magna, which goes to the eye-ball. 

 This efferent pseudobranehial artery is formed by the two vessels 

 marked k and h in Hyrtl's figure of Raja clavata, and in the specimen 

 of Raja radiata here used for illustration the vessel c of Hyrtl's figure 

 joins and fuses with the vessel k about midway of its length. 



In a recent work on the skulls of Pristis and Pristiophorus, 

 Ludwig Hoffmann (1912) describes carotid, efferent pseudobranehial 

 and pituitary canals that apparently differ from those in Raja only 

 in that the vertical section of the carotid canal is single throughout 

 its entire length instead of being double in its dorsal portion, but 

 Hoffmann interprets the arrangement of the related arteries quite 

 differently from what I do. According to his descriptions, which relate 

 primarily to Pristiophorus but doubtless apply equally to Pristis, 

 the anterior carotid (efferent pseudobranehial) artery first gives off the 

 arteria ophthalmica and then perforates the side wall of the cranium 

 and enters the cavum cranii. There it is said to run postero-mesially 

 and to meet and anastomose with its fellow of the opposite side, in 

 the median line, thus forming a transverse commissure. Hoffmann 

 then says (1. c. p. 295): "In der Mitte dieser Anastomose mündet nun 

 der oben erwähnte unpaare Ast der Carotis posterior, nachdem er 

 die Basis cranii durchsetzt hat. Unmittelbar nach ihrem Eintritt 

 in die Cranialhöhle entsendet die Carotis posterior nach vorn die 

 Arteria cerebrahs." Just what the arrangement here is, and whether 

 the cerebralis arteries are given off from the unpaired branch off the 



