154 SUB-CLASS ELASMOBRANCHII. 



organ ; viviparous. Rhinobatus Bl. and Schn., guitar-fishes, tropical and 

 sub-tropical, and fossil from the upper Jurassic ; Rhynchobatus M. and 

 H., Ind. Ocean to China ; Trygonorhina M. and H., Australia ; Zapteryx 

 Jor. and Gilb., Peru ; Platyrhinoidis Gar., California. Extinct genera : 

 Asterodermus Ag., Belemnobatis Thiol., Upper Jurassic. 



Fam. 3. Torpedinidae. Trunk a broad, smooth disc ; tail with 

 rayed dorsal (absent in Temera) and caudal fins and a longitudinal fold 

 on each side, without serrated dorsal spine ; anterior nasal valves con- 

 fluent into a quadrangular lobe. An electric organ between the pectoral 

 fins and the head. Eocene to the present time. Torpedo Dum. (Narco- 

 batis Blainv.), large specimens (width from 2 to 3 ft.), can disable 

 a man. Med., Atl., Ind. Oceans ; T. nobiliana Bon., spiracles not 

 fringed at their margins ; on flat sands or mud, 40-50 fathoms ; T. mar- 

 morata Risso, spiracles fringed ; Narcine Henle, trop. and sub-trop. ; 

 Hypnos Dum., Australian ; Discopyge Tschudi, Peru ; Astrape M. and H., 

 Ind., S. Afr. ; Temera Gray, E. Ind. 



Fam. 4. Rajidae. Skates. Disc broad, rhombic, generally with 

 asperities or spines ; tail with longitudinal fold on each side ; pectorals 

 extend to snout ; no electric organ or serrated caudal spine ; oviparous ; 

 sexual differences are frequently observable, in colour, form of teeth and 

 arrangement of spines. Cretaceous to the present tune. Raja Art., tail 

 distinct from disc, pectoral fins not extended to front end of snout, caudal 

 fin rudimentary ; may attain width of 6-7 ft. ; in some species the teeth 

 of the male are sharper than in the female, and in all species the males 

 are armed with patches of claw-like retractile spines on the upper side 

 of the pectoral fin ; seas of both hemispheres ; R. batis L., skate, oviposi- 

 tion from May to September, to 6-7 ft. ; R. macrorhynchus Raf., flapper 

 skate ; R. alba Lacep., white skate, to 8 ft. ; R. oxyrhynchus L., long- 

 nosed skate ; R. fullonica L., Fuller's ray, shagreen skate ; R. clavata L., 

 thornback ; R. maculata Montagu, homelyn ray, spotted ray ; R. micro- 

 cellata Montagu ; R. radiata, starry ray ; R. circularis Couch, sandy ray. 

 Psammobatis Giinth., South America ; Sympterygia M. and H. ; Platy- 

 rhina M. and H. Extinct genus : Cyclobatis Eg., Cretaceous. 



Fam. 5. Trygonidae. Sting-Rays. Pectorals continued to and 

 confluent at end of snout ; tail long and slender, without lateral folds ; 

 vertical fins none or imperfect, often replaced by strong serrated spine. 

 Tertiaries to present time. Urogymnus M. and H., Ind. Oc. ; Ellipe- 

 surtis Schomburgk ; Trygon Adanson (Dasyatis Raf.), tail with long 

 serrated spine, temp, and trop. ; T. pastinaca, sting ray, sandy ground 

 near land, caudal spine causes severe wounds ; Taeniura M. and 

 H., Indian seas, fresh-waters of trop. America ; Urolophus M. and H., 

 Australian and Caribbean seas ; Pteroplatea M. and H., temp, and 

 trop. seas. 



Fam. 6. Myliobatidae. Eagle-rays. Disc broad with large pectoral 

 fins which are not present at the sides of the head, but reappear as at the 

 extremity of the snout as a pair of detached fins ; teeth hexagonal, flat, 

 tesselated ; tail long, thin, whip-like ; viviparous. Myliobatis Cuv., 

 snout with a soft prolongation with fin rays ; temp, and trop. seas ; 

 M. aquila L., mill-skate, whip-ray, eagle-ray ; Aetobatis M. and H., 

 tropical seas ; Rhinoptera Kuhl, trop. and sub-trop. seas ; Dicero- 

 batis Blainv. (Aodon Lac.) (Cephaloptera Dum.), head with a forwardly- 

 pointing horn-like projection on either side ; attain great size ; temp, 

 and trop. seas ; D. giornae. Ceratoptera M. and H. (Mania Bancroft), 



