21. TRYGONID^l. 45 



head, middle of back, and on tail. Under side smooth, except ante- 

 riorly. Teeth -. Color brown, everywhere strongly variegated with 

 light and dark colors ; a black spot at base of each pectoral, surrounded 

 by a pale ring, and this by a black ring 5 numerous black spots of various 

 sizes, some of them ocellated, scattered over the body ; head with black 

 cross-bars. 



Disk one-fifth broader than long ; the length of tail more than half 

 the width of disk ; the snout 4 in length of disk, and 2 times the inter- 

 orbital width ; the snout is as long as in binoculata, but much wider, 

 appearing blunt and short. L. 2- feet. Bay of Monterey, California ; 

 locally abundant. 



(Jordan & Gilbert, Proc. U. S. Nat. Mus. 1880, 133.) 



FAMILY XXI. TRYGONID^. 



(The Sting Eays.) 



Disk usually more or less broader than long ; the pectoral fins uninter- 

 ruptedly confluent in front, forming the tip of the snout ; tail variously 

 formed, usually whip-like, sometimes short and stout, sometimes bearing 

 a single dorsal or caudal fin, but never with two dorsals. Usually one or 

 more vertical folds of skin on the tail, rarely a lateral fold. Tail generally 

 armed with a large, sharp, retrorsely serrate spine on its upper surface, 

 toward the base (two or three spines occasionally present). Ventral 

 fins not ernarginate. Skin smooth or variously prickly or spiuous, rough- 

 est on the adult. No differentiated spines on the pectorals in the males, 

 the sexes being similar. Mouth rather small,. Teeth small, paved, usu- 

 ally more or less pointed or tubercular. Nostrils near together ; nasal 

 valves forming a rectangular flap, which is joined to the upper jaw by 

 a narrow frenum. Spiracles large, placed close behind the eyes. Skull 

 not elevated, the eyes and spiracles superior. Ovo viviparous. Genera 

 about 10 ; species 50. Found in most warm seas, some of them in the 

 fresh waters of Central and South America. The large spine on the 

 muscular tail is capable of inflicting a severe and even dangerous wound. 



(Tnjyonidw Giiuther, viii, 471-488.) 



* Tail stout, provided with a rayed caudal tin UROLOPHDS,* 38. 



** Tail slender, -without caudal flu. 



t Tail very short, shorter than the broad disk PTEROPLATEA, 39. 



ti Tail whip-like, longer than the disk - - - DASYATIS, 40 



* In the key to the families of Raim, on page 36, the character assigned to Trygonida, 

 "Tail very slender, whip-like, its fius, if any, small and near its base," does not apply 

 to the genus Urolophus, and should be modified. All the " Pachynra" have two dor- 

 sals and a trace at least of a caudal tin. In the Masticura" one or more of these fins 

 are obsolete, and a serrated caudal spine is generally present. 



