21. TRYGONID^. 45 



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

 riorly. Teeth |-f. 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 ; numerous black spots of various 

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

 cross-bars. 



Disk one-lifth 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 hinoculatu, but much wider, 

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

 locally abundant. 



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



Family XXI.— TRYGONID^. 



{The Sting Bays.) 



Disk usually more or less broader than long ; the pectoral lins 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 flu, 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 

 tins not emargiuate. Skin smooth or variously prickly or spinous, rough- 

 est on the adult. ISo diflerentiated 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 

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



{Trygonidw Giinther, viii, 471-488.) 



*Tail .stout, provided with a rayed caudal fin ITkoloI'HUS,* 38. 



**Tail slender, without caudal liu. 



t Tail very short, shorter than the Iiroad di.sk I'tkuoplatea, 39. 



tt Tail whip-like, louj^er than the di.sk Dasyatis, 40 



* In the key to the families of liaia;, on page 36, the character assigned to TrygonidcB, 

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

 to the genus Urolophim, and should be modified. All the "raehyura" have two dor- 

 sals and a trace al least of a caudal fin. In tht^ " Masticnra" one or more of these fins 

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



