“ae ure? i 
v 
Variations in Afferent Branchial Arteries of the Skate. 239 
Fig. 6 presents a new case. The second afferent branchial is again 
affected, but in this case it arises as a separate vessel from the ventral aorta. 
Fig. 7 represents a second specimen in which the abnormality affects 
both sides, but in this case it is unsymmetrical, and in that respect presents 
a contrast to Fig. 2. It combines the two last conditions described, closely 
resembling Fig. 6 on the left side of the specimen and Fig. 5 on the right. 
A comparison of these variations of the afferent branchial system in the 
skate with the usual condition displayed in some other Elasmobranchs, 
suggests that they should be regarded, not as actual malformations, but 
rather as indicating an unstable and fluctuating condition in the more 
specialised group of the sub-class. The origin of the first two afferent 
Fic. 6. Raia, 
Species and sex not recorded. Fie. 7. Raia circularis 6. 
vessels as branches of an innominate artery, is a not unusual EHlasmobranch 
condition which fata shares, for example, with Scyllwwm and with 
Chlamydoselachus, which latter is. considered by Ayers! as a primitive type 
in respect of its arterial system. When, however, as an abnormality in Raza, 
the second affereut branchial arises independently from the ventral aorta, 
the condition presented is the same as that exhibited by J/ustelus. With 
regard to the three posterior afferents, the clumping together of these vessels 
in faia as branches of a posterior innominate, may be regarded as a 
progressive departure from more usual Elasmobranch conditions. Finally, 
the tendency, as an abnormality in Raia, for as many as four afferent vessels 
to diverge from near the base of the ventral aorta, recalls in some degree 
the afferent system of the Dipnoan Ceratodus, in which the ventral aorta 
is so much shortened that all four afferent vessels arise close together 
immediately anterior to the conus arteriosus. 
1 H. Ayers, “The Morphology of the Carotids, based on a study of the Blood-vessels 
of Chlamydoselachus anguineus (Garman.),” Bull. Mus. Comp, Zool , Harvard, xvii., 1889. 
