ANGEL-FISH. 39 



and the large size of the pectoral fins, and the forward production 

 of their bases towards (but not reaching) the head, suggest an 

 approach to the members of the next suborder, the Raii, although 

 the indication is probably fallacious. The dorsal fins are without 

 spines, and are set upon the tail part of the body. Small 

 tubercles occur embedded in the skin ; the teeth are conical and 

 pointed (see jaws 91) ; the vertebrae (see vertebrae 90) are tecto- 

 spondylic, this term signifying that of the secondary calcified 

 laminae on the outside of the primary double-cone calcification 

 immediately around the constricted notochord, the concentric 

 laminae preponderate over the radiating laminae. In the Angel- 

 fish the concentric lamina? are very numerous and closely set ; in 

 the extinct species they are less numerous. This type of vertebra 

 occurs also in the Saw-fishes and Rays, though in a less pronounced 

 form (see vertebra of Rata, 113, Wall-case 3). The Angel-fish 

 grows to a length of five feet^ and is wide-spread throughout the 

 tropical and temperate seas. 



The Petalodontidae (represented by teeth of Petalodus, 92, and 

 Polyrhizodus, 93) are extinct fishes, allied to the Angel-fish, which 

 flourished in Carboniferous and Permian times. The body was 

 moderately depressed, the pectoral fins large and continued 

 forward towards the head. The teeth were compressed antero- 

 posterior^, and formed a close pavement over the surface of the 

 jaw. 



In Pristiophorus, 94, the sole genus of the family Pristiophoridae, Pristio- 

 the elongation of the snout to form a rostrum, and the presence of 

 teeth along its edges, suggest an affinity with the Pristidae or Saw- 

 fishes, the first family of the next suborder, but the body is 

 scarcely depressed, the gill- slits are lateral in position, the pectoral 

 fins are of moderate size, and their bases show no tendency to 

 spread towards the head. On the other hand, the enlargement of 

 the prepalatine cartilages of the skull which is observed in the 

 Pristiophoridae is a feature which in the Rays is definitely 

 associated with the extension of the front of the pectoral fin around 

 the edge of the head. A pair of long barbels occur on the under- 

 side of the 'saw/ The teeth of the mouth are small, with a 

 conical cusp on a broad base. These fishes occur in the seas of 

 Japan and Australia, and attain to no great size. 



