228 



HARDWICKE'S SCIENCE-GOSSIP. 



the possession of a greatly elongated snout (fig. 161), 

 having the form of a nearly flat blade, and armed 

 with a row of teeth fixed in sockets on each edge. 

 More or less imperfect fragments of this powerful 

 weapon are the only fossil remains ordinarily met 

 with, and all these at present known evidently belong 

 to the living genus, Pristis ; they occur in the Ter- 

 tiary formations both of Europe and America, and 

 the Middle Eocene of Bracklesham has yielded some 

 good examples. Of the latter, the most common are 

 detached rostral teeth (fig. 162), but a few specimens 

 of the snout itself are also known, and two interesting 



depressed as in the most typical rays, but there is a 

 relatively long and slender tail. Spathobatis is an 

 Oolitic genus, and the living Rhinobatus first occurs 

 in the Cretaceous of the Lebanon. 



Torpedinid^e. 



The " Torpedoes " — remarkable, as is well known, 

 for their power of producing electric shocks — are 

 represented at the present time by several genera, 

 chiefly in tropical and sub-tropical seas, but the 

 pakeontological record has hitherto revealed only 



Fig- 155.— Tooth of Polyrhizodus 

 radicans. 



Fig. 156. — Teeth of 

 Pet a lor hy nek us 

 psittacinus. 



Fig. 157.— Dental series in jaw of Fig. 159.— Tooth 

 Janassa. (.After Hancock and of Ctenoptychius 



Howse.) pectinatus. 



T "> - 



Fig. 158. — Diagram showing 

 succession of teeth in jaw 

 of Janassa. (After Han- 

 cock and Howse.) 



Fig. 162.— Rostral tooth 

 of Pristis Hastingsice 

 (half nat. size). 



Fig. 163.— Dermal tubercle 

 of Raja antiqua. 



Fig. 160. — Sketch of skeletal 

 parts of Sqnaloraja poly- 

 spondyla (one quarter nat. 

 size), n, rostral prolonga- 

 tion ; s, spine ; o, orbits ; 

 /, pectoral fins ; v, ventral 

 fins. 



Fig. 161. — Lower aspect of head 

 and rostrum of Pristis. (After 

 Owen.) 



fragments are exhibited in the British Museum. 

 These fossils are referred to about four species, but 

 the most important are P. Hastingsice (fig. 162), and 

 P. contortns — the latter with the rostral teeth slightly 

 twisted. 



Rhinobatid^e. 



The Rhinobatidae do not appear to be represented 

 in British formations, but their remains, as found in 

 the Lithographic Stone (Upper Oolite) and later 

 deposits on the Continent, are among the most 

 beautifully preserved of fossil Plagiostomes. They 

 possess no dorsal spine, and the body is not so 



very few of their extinct progenitors. None are 

 known to occur in British strata, but a very perfect 

 example, from the Cretaceous rocks of Mt. Lebanon, 

 was described long ago by Sir Philip Egerton,* and a 

 few similar relics have been met with in the Eocenes 

 of Monte Bolca, near Verona. 



Rajid^e. 



This is the family of Rays-proper, comprising 

 several genera that agree in possessing a much- 

 depressed body, more or less protected by hard 



* Proc. Geol. Soc, vol. iv. (1S84), p. 446, pi. V. 



