RAYS. 335 



Tenth Family — PEisTioPHOEiDiE. 



The rostral cartilage is produced into an exceedingly long, 

 flat lamina, armed along each edge with a series of teeth (saw). 



These Sharks resemble so much the common Saw-fishes 

 as to i)e easily confounded with them, but their gill-openings 

 are lateral, and not inferior. They are also much smaller in 

 size, and a pair of long tentacles are inserted at the lower 

 side of the saw. The four species known (Pristiophorus) occur 

 in the Australian and Japanese seas. 



Sgualoraja, from the Lias, is supposed to have its nearest 

 affinities to this family. 



B. Batoidei — Bays. 



In the typical Bays the body is excessively depressed, 

 and forms, with the expanded pectoral fins, a circular or 

 sub-rhomboidal disk, of which the slender tail appears as a 

 more or less long appendage. In the two families which we 

 shall place first (Fristidce and Bhinohatidce), the general habit 

 of the body still resembles that of the Sharks, but the gill-open- 

 ings are ventral, as in the true Bays ; the anal fin is invariably 

 absent, and the dorsal fins, if developed, are placed on the 

 tail. The mode of life of those fishes is quite in accordance 

 with the form of their body. Whilst the species with a 

 shark-like body and muscular tail swim freely through the 

 water, and are capable of executing rapid and sustained 

 motions, the true Bays lead a sedentary hfe, moving slowly 

 on the bottom, rarely ascending to the surface. Their tail 

 has almost entirely lost the function of an organ of locomo- 

 tion, acting in some merely as a rudder. They progress solely 

 by means of the pectoral fins, the broad and thin margins of 

 which are set in an undulating motion, entirely identical 

 with that of the dorsal and anal fins of the Pleuronectidce. 

 They are exclusively carnivorous, like the Sharks, but unable 



