21. TRYGONID^. 
45 
head, middle of back, aud ou tail. Under side smooth except ante- 
riorly. Teeth If. Color brown, everywhere strongly variegated with 
light and dark colors ; a black spot at base of each i)ectoral, 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 lengtli of disk, aud 2 | times the inter- 
orbital width 5 the snout is as long as in binoculata, but much wider, 
appearing blunt aud short. L. 2| feet. Bay of Monterey, California ; 
locally abundant. 
(Jordan & Gilbert, Proc. U. S. Nat. Mus. 1880, 133.) 
Family XXL— TRYGONID^. 
{The Sting Bays.) 
Disk usually more or less broader than long 5 the pectoral fins uninter- 
ruptedly confluent in front, forming the tip of the snout ; tail variously 
formed, usually whip-like, sometimes short aud 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, sharii, retrorsely serrate spine on its upper surface, 
toward the base (two or three spines occasionally iiresent). Ventral 
fins not emargiuate. Skin smooth or variously prickly or spinous, rough- 
est on the adult. Xo difilerentiated 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. INostrils near together; nasal 
valv^es 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. Ovoviviparous. Genera 
about 10 ; species 50. Found in most warm seas, some of them in the 
fresh waters of Central and Soutj^ America. The large spine on the 
muscular tail is capable of inflicting a severe aud even dangerous wound. 
{Tnjgonklcc Giiutlier, viii, 471-488.) 
*Tail stout, provided witli a rayed caudal fin Urolophus,* 38. 
**Tail slender, without caudal fin. 
tTail very short, shorter than the broad disk Pteroplatea, 39. 
tt Tail whip-like, lono-er than the disk Dasyatis, 40 
* In the key to the families of Ilam, on page 3(5, the character assigned to Trygonidw, 
“Tail very slender, whip-like, its fins, if anj*, small and near its base,” does not apply 
to the genus Urolophus, and should be modified. All the “Pachyura” have two dor- 
sals and a trace at least of a caudal fin. In the “ .Masticura” one or more of these fins 
are obsolete, and a serrated caudal spine is generally present. 
