22 SELACHII: RALE. v. 



21. TORPEDO Dumeril. 



30. T. occidentalis Storer. TORPEDO. CRAMP-FISH. NUMB- 

 FISH. Black, with obscure darker blotches ; spiracles with entire 

 edges. L. 3 to 5 feet. Cape Cod S. ; not common. 



FAMILY XVI. DASYATID^E. (THE STING-RAYS.) 



Disk broad, the pectorals confluent anteriorly, forming tip of 

 snout ; tail, usually whip-like, sometimes short and stout, with or 

 without fins, but never with two dorsals. Tail usually armed with 

 a sharp, retrorsely serrate spine above, near the base (this often 

 duplicated and sometimes wanting) : ventral fins entire. Skin 

 smooth or variously rough, the adult roughest. Mouth small, with 

 small teeth. Sexes similar. Genera 10, species 50, in most 

 warm seas. The large spine or " sting " on the tail in most species 

 may inflict a dangerous wound. 



a. Tail slender, whip-like, without caudal fin, longer than the disk; "sting" 



on tail strong DASYATIS, 22. 



aa. Tail very slender and short, shorter than the very broad disk : sting 

 minute or wanting PTEROPLATEA, 23. 



22. DASYATIS Rafinesque. (Trygon Adanson.) 



(Sau-vs, shaggy or rough ; {farts, skate.) 

 a. Tail with a fold on its lower margin only, the upper edge rounded. 



31. D. centrums (Mitchill). COMMON STING-RAY. CLAM- 

 CRACKER. STINGAREE. Snout not prominent ; disk a little wider 

 than long; tail usually not quite twice length of disk. Adult 

 with some stellate tubercles on back and tail. Color olive-brown. 

 L. 12 feet. Cape Cod S., common, (nevrpov, spine; ovpd, tail.) 

 aa. Tail with a fold of skin on its upper as well as lower margin. 



32. D. say (Le Sueur). SOUTHERN STING-RAY. WHIP- 

 PAREE. Snout not prominent ; disk a little wider than long ; tail 

 nearly twice length of disk. Body and tail without large spines. 

 N. Y., S. (To Thomas Say, a distinguished zoologist.) 



23. PTEROPLATEA, Miiller & Henle. 



33. P. maclura (Le Sueur). BUTTERFLY RAY. Disk nearly 

 twice as broad as long, three times as long as tail ; sting on tail 

 usually obsolete. Olive-brown, finely marbled and speckled ; tail 

 with four dark blotches : front edge of disk with pale half-circular 

 spots. Va. S. (To William Maclure.) 



FAMILY XVII. AETOBATID^B. (THE EAGLE RAYS.) 

 Pectoral fins interrupted, reappearing on tip of snout as one or 

 two detached appendages or cephalic fins ; skull somewhat elevated, 

 so that eyes and spiracles are lateral ; teeth large, flat, hexangular, 



