Alopias vulpes. 485 
not peculiar to the Plagiostome fishes; it has been id in 
Esox lucius, in Silurus glanis, and in the sturgeon. 
DISSECTION OF A FEMALE FOX SHARK. (THRESHER OR SWINGLE- 
TAIL.) (ALOPIAS VULPES.) 
The specimen was quite small; total length 5 feet 1 inch, 
of which the body was 2 feet 6 inches, the upper lobe of tail 
2 feet 7 inches. 
The only difference in the heart of this fish from that of 
the Scymnus was in the valves of the branchial artery ; the 
upper system, consisting of three semilunar valves, was 3 an 
inch from the heart; the lower system consisted of three lon- 
gitudinal bands of rough valves, each band having only two 
valves, one above the other, instead of four as in the Scymnus. 
The ventricle was 1 inch in diameter; the walls nearly half 
an inch thick. 
The liver consisted of two lobes; the left 16 inches long, 
the right 9 inches ; width 3 inches. 
The principal differences were in the alimentary canal, this 
being more simple in the present fish. 
The mouth and branchial arches were quite rough to the 
finger, passed. from below upwards; but smooth in the oppo- ` 
Site direction ; thus securing their hold of their prey. 
The cesophagus was 2 inches long; cut open, 24 inches 
Wide : divided into about a dozen prominent longitudinal folds. 
The cardiac orifice was 24 inches wide, cut open ; having 
à well marked fold which would act as a valve to retain the 
Contents of the stomach. Stomach 1 foot long; 7 inches 
Wide, cut open ; in the upper half, both the longitudinal and 
Circular fibres very distinct. Pylorus opened half an inch 
from the bottom of stomach ; ; its valve well marked ; half an 
inch wide, cut open. From pylorus to anus 1 foot 10 inches ; 
from pylorus to spiral portion 9 inches ; length of spiral 9 
inches ; from end of spiral to anus 4 inches. Between the 
pylorus and the spiral portion, the intestine was only half an 
inch wide, cut open ; very thin ; its fibres running obliquely ; 
