XVII ELASMOBRANCHII—-SELACHII—-BATOIDEI 457 
and crescentic. Vertebrae tectospondylic. Teeth conical and 
pointed. A single species only is known. 
Rhina squatina, the Angel-Shark or Monk-Fish (Fig. 261), is 
intermediate between the ordinary Sharks and the Skates and 
Rays, both in external appearance and internal structure, but 
is more Ray-hke than Shark-like in its habits. Within the 
temperate and tropical regions of both hemispheres it is almost 
cosmopolitan in its distribution, frequenting the coasts of Europe, 
including the British Isles, the Atlantic and Pacific coasts of 
North America, and the shores of South Austraha and Japan, 
The Angel-Shark is viviparous, producing about twenty young at 
a time. Not rarely it grows to a length of 5 feet. 
The family ranges from the Upper Jurassic to the present 
time. Species of Aina are represented by more or less com- 
plete skeletons in the Lithographic Stone of Bavaria, and in the 
Upper Cretaceous of Westphalia and Mount Lebanon, and by 
teeth and vertebrae in the English Chalk, as well as in different 
European Tertiary formations. 
Fam. 15. Pristiophoridae.—Prenasal portion of the head 
and cranium produced into a long flattened rostrum, furnished 
with a pair of long tentacles on its under surface, and, as in 
Saw-Fishes, with a series of large, tooth-like, dermal denticles, of 
equal or unequal size, along each of its lateral margins. Two 
dorsal fins, without spines, the first in front of the pelvics. No 
anal fin. Pectoral fins large, distinct from the head and trunk, 
with a contracted base. Spiracles large and crescentic. Teeth 
small, with a conical cusp and a broad base. 
These singular Sharks closely resemble the true Saw-Fishes 
(Pristidae), but they differ in the lateral position of their gill- 
clefts, the presence of rostral tentacles, and their smaller size. 
The few species known belong to the genus Pristiophorus, and 
are confined to the Australian and Japanese seas. 
Pristiophorus is represented in the Upper Cretaceous of 
Mount Lebanon, and in the Miocene deposits. 
Sub-Order 2. Batoidei. 
Body generally discoidal or rhombic in shape, the axial 
portion being formed by the flattened head and trunk, and the 
lateral portions by the enormously expanded pectoral fins, which 
