80 BULLETIN OF THE 



erate length, and puts out directly toward the eye. On the crown the cranials 

 are straight until opposite the fontanelle, where they make a shallow outward 

 curve. The rostrals descend near the end of the rostrum. Starting down 

 and backward, the orbitals make a broad curve around the eye until beneath 

 it, where they become longitudinal and run more than a diameter forward 

 from the orbit, before turning down and back, parallel with themselves, to 

 join the angular. Both angular and jugular are long. From the angular the 

 oral bends back around the mouth; it is not continuous across the symphysis. 

 The long orbito-nasal bends down under the fore part of the eye before becom- 

 ing longitudinal. Above the nostril the subrostral turns abruptly toward the 

 nasal, in which there is no perceptible curve. The median is elongate and 

 longitudinal. At the median the rather short prenasals bend outward, then 

 turn forward to join the rostrals. 



The type is characterized by absence of anal or caudal bends, by an elon- 

 gate occipital, a slight curvature in the cranials, a longitudinal loop in the 

 suborbitals, a prominent curve in the subrostrals, absence of a nasal curve, 

 and by the junction of oral and angular. 



Alopias. 



Alopias vulpes (Plates XII., XIII.). A very great development of the 

 canal system obtains in this Shark. There is no great difference in the main 

 tubes from what may be seen in allied genera ; it is in the enormous number, 

 the length, and the amount of branching of the tubules, that unusual features 

 are most patent. 



Forward the lateral bends upward a little ; at the base of the tail it fol- 

 lows the vertebral axis, keeping its position near the middle of the muscular 

 portion, and ends a little in advance of the notch in the hinder extremity. 

 Throughout the entire length the tubules are closely placed on the sides. 

 Anteriorly, on the thorax, they are directed toward the back. Nearly all of 

 those on the abdominal region are extended toward the belly. From the base 

 of the ventrals to the end of the anal the tubules have numerous branches, 

 some of which pass upward and others downward. On the tail the tubules 

 are sent toward the lower edge of the fin. 



The aural is long; in prominent curves it bends back in the middle and 

 forward at each end. The occipitals are short. In the cranials the curves are 

 shallow. At the crown the orbital starts back and down ; as a post-orbital it 

 is vertical; and in the suborbital it sinks below the eye. Slightly in advance 

 of the eye the suborbital turns back, and not far from the centre of the orbit, 

 over the front edge of the mouth, is the union with the angular. The latter 

 is of medium length. An uncommon arrangement of the jugular is seen here: 

 the tube is long and passes below the gill apertures. The oral is elongate and 

 connected with the angular ; it makes a sharp bend around the corners, and is 

 divided by a narrow interspace in the middle, behind the symphysis. At the 



