BLOOD-VESSELS OF MUSTELUS ANTARCTICUS. 
687 
The ventral aorta (Plate 34, figs. 1 and 2; Plate 37, fig. 18 ; V. Ao.) of Mustelus 
antcircticus presents no points of special interest. Immediately after its origin from 
the short conus arteriosus ( C . Art.) it gives off on each side a short outwardly-directed 
trunk which almost immediately divides into the afferent arteries of the fourth and 
fifth gills (Af. hr. A. 4 and Af. hr. A. 5), that is, those borne by the third and fourth 
branchial arches respectively. Passing forwards, the ventral aorta gives off a single 
trunk on either side to the third gill ( Af. hr. A. 3), and, at its anterior termination, 
divides into two vessels, each of which passes directly outwards, soon dividing into 
the first and second afferent branchial arteries (Af. hr. A. 1 and Af. br. A. 2). Of 
these the former (Af. br. A. l) is distributed to the liyoidean hemibranch,* the latter 
(Af. br. A. 2) to the gill of the first branchial arch or first complete gill. 
The precise position of the afferent artery with regard to the various constituents 
of the gill is best seen in transverse section and will be described immediately (p. 688). 
2. The Efferent Branchial Arteries, Epibranchial Arteries, and Dorsal Aorta. 
a. Efferent Branchial Arteries. 
Branchial Veins, Monro (16), Owen (19), Huxley (10), Gegenbaur (7), 
Rolleston (24), Macalister (13), Balfour (2). 
Kiemenvenen, Hyrtl (11), Stannius (25). 
Vence branchiales, Muller (17). 
Arteres epibrancliiales (in part), Milne Edwards (14). 
Epibranchial arteries, branchial veins, Claus (4). 
b. Epibranchial Arteries. 
Aortenwurzeln, Hyrtl (11), Dohrn (5). 
Radices aortce, Wiedersheim (26). 
Vence branchiales communes, Muller (17). 
Arteres epibrancliiales (in part), Milne Edwards (14). 
c. Dorsal Aorta. 
Trunk of descending aorta, Monro (16). 
Aorta descendens, Muller (17). 
Aorta, Hyrtl (11), Stannius (25), Owen (19). 
Aorta abdominalis, Wiedersheim (26). 
Aorta dor sale, Milne Edwards (14). 
Dorsal aorta, Huxley (10). 
Dorsal aorta, aorta, descendens, Claus (4). 
As usual in Plagiostomes, which in this, as in many other points of structure, differ 
from all other amphirhinous fishes, there is an efferent branchial artery for each 
* I have adopted (in 28) this very convenient word as the equivalent of Milne Edwards’s “demi- 
branchie.” It means the whole set of gill-filaments on one side of a gill ponch in a Cyclostome or an 
Elasmobranch, A complete gill, composed of two hemibranchs, maybe appropriately termed a holobranch. 
