SQUATINA AND PRISTIS gI 
The different families of the existing sharks appear to 
to have been already differentiated during the early Meso- 
_ zoic times. The ancient shark-like form had then given 
_- place to the flattened and rostrated types, adapted to the 
Fig. 96 B. — The Greenland shark, Lemargus borealis,L. X ds. (After GUNTHER.) 
conditions of bottom living and to the special ‘character of 
their shell-fish or crustacean diet. 
One of the earliest offshoots from the main selachian 
stem appears to have been Sgwatina (Fig. 97), popularly 
known as the monk-fish, or angel-fish. As early as the 
Mesozoic times it was existing, differing but little from the 
recent species. Its general shape is shark-like, although its 
eh te 
_ Fig. 97.-—The monk-, or angel-fish, Rhina squatina, &. x Atlantic, 
Mediterranean, Pacific. 
head and trunk are clearly depressed. This, together with 
its enlarged pectoral fins, enables it to take a position 
closer to the bottom. 
The recent saw-fish, Pristis (Figs. 98, 98 A), is next to 
