xvi ELASMOBRANCHII—BATOIDEI 401 
represented by complete skeletons in the Lithographic Stone of 
Bavaria, the Upper Cretaceous of Mount Lebanon, and the Upper 
Eocene of Monte Bolea. Zrygonorhina occurs in the Eocene. 
Fam. 3. Raiidae (Skates or Rays).—The endoskeletally 
supported portions of the large pectoral fins extend along the 
lateral margins of the trunk and head from the pelvic fins to 
the snout, and are confluent therewith, forming the lateral por- 
tions of a large rhombic disc. The tail is slender, and sharply 
marked off from the trunk. Usually two small dorsal fins on 
the tail. Caudal fin small or absent. No serrated spine on the 
i ii TAN AN 4, 
Mie Ke se 
\\ BNI & gers 
TE AR * 
PAY Vos 
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vil 
JA TAN 
Fic. 264.—Raia murrayi, from Kerguelen Island. A, male; B, female. 
(From Giinther.) 
tail. Caudal electric organs are often present. Larger or 
smaller denticles or spines are generally present on the skin. 
Oviparous. Egg-cases four-horned, without tendrils. Four 
genera and from thirty to forty species. _ Found in all temperate 
seas, a few ranging into deep water. 
The great majority of the species belong to the genus Lava 
(Fig. 264), which chiefly inhabits temperate seas, but 1s more 
abundant in the northern than in the southern hemisphere, and 
approaches nearer to the Arctic and Antarctic regions than any 
other Batoidei. The colour of the upper surface of the body is 
closely assimilated to that of the sandy or gravelly bottom on 
