ANGEL- AND SAW-FISHES. 
535 
becomes so intent on its occupation as to allow itself to be harpooned without 
attempting to escape. Four living young are stated to be produced at a birth. 
Finally, we have the spiny shark (.Echinorhinus spinosus ) of the Mediterranean 
and Atlantic, which while agreeing with the last in the small size of the tins and 
the absence of spines to the dorsals, differs by the teeth being alike in both jaws, 
and by the presence of large rounded tubercles scattered over the skin; the body 
being very bulky, and the tail short. This shark lives at considerable depths, and 
but rarelv comes to the surface. 
%/ 
The Extinct Petalodonts, —Family Peta l on ontieuE. 
The extinct genera Petalodus and Janassa, together with several other allied 
types from the Carboniferous rocks, represent a family apparently connecting the 
last with the more typical rays. In these fishes the body is moderately depressed, 
and the pectoral fins are large and continued anteriorly towards the head. The 
teeth, which generally have large roots, are compressed from front to back, with the 
crown more or less bent backwards, and either with a sharp cutting-edge, or very 
blunt. In the mouth they were arranged in straight rows to form a pavement. 
The Angel-Fish,— Family Sqtja tinid^e. 
The sole existing representative of its family, the angel-fish, or monk-fish 
(Squcitina vulgaris), constitutes, so far as external form is concerned, a kind of 
connecting link between the sharks and the rays. Having the body as much 
depressed as in some of the latter, the angel-fish differs in the nearly terminal 
position of the mouth, and also in the circumstance that while the basal portion of 
the pectoral fins is much produced forwards, it does not extend so far as to join 
the head. The wide gill-clefts are lateral in position, and partly covered by the 
base of the pectoral fins; the spiracles are wide and placed behind the eyes ; and 
the teeth are conical and pointed. Spines are wanting to the dorsal fins, which are 
situated on the tail; and the skin is studded with tubercles. Not unfrequently 
growing to a length of at least 5 feet, the angel-fish has an almost cosmopolitan 
distribution, and is by no means uncommon on the British coasts, more especially 
in Scotland. In colour it is mottled chocolate-brown above, and whitish beneath, 
and except that it produces living young, which may number as many as 
twenty at a birth, its general habits are similar to those of the rays. Fossil 
species of angel-fish range through the Tertiary and Cretaceous strata to the 
upper Jurassic. 
The Saw-Fishes,—F amilies Peistiophoeidn and Peistidn. 
Unique among the whole'class on account of the production of the upper jaw 
into a long flattened beak, furnished on either edge with a series of large, sharp, 
and pointed teeth, set in distinct sockets at a considerable distance from one 
another, the saw-fishes form two well-defined families, the first of which approxi¬ 
mates to the sharks in the position of the gill-clefts, while the second agrees with 
