90 On the generic characters 



2. Platyrhina, Nob. The nasal valve extends beyond the inner corner 



of the nostril, nearly to the middle of the snout, which is obtuse, 

 and the body orbicular, approaching Torpedo. (1 sp.) 



3. Trygonorrhina, Nob. Tail of Rhinobatus, with the nose of Trygon. 



(1 sp.) 



. The TORPE DINES constitute four genera -.—Torpedo, 

 s. s. (3 sp.) Narcine, Henle, (4 sp.) Astrape, Nob. (T. ca- 

 pe nsis and dipterygia, aut.) and Temera, Gray. (1 sp ) 



The true RAIJE contain three genera : — 



1. Raia, Cuv. (17 sp.) 



2. Sympterygia, Nob. Tail of Raia ; the pectoral fins, which do not 



reach to the keel of the snout in the true Raice, are, in the Sympter- 

 ygice, extended to the mesial line, touching each other with their in- 

 ner edges. The abdominal fin is not divided into two lobes by an 

 incision, as it is in Raia. (1 sp.) 



3. Uraptera, Nob. diners from Raia only by the want of a caudal fin. — 



(1 sp.)* 



The genus TRYGON, Cuv. has become a large family, 

 containing the following genera : — 



Trygon, s. s. are the Sting Rays, the teeth of which are elliptical, and 

 have a transverse wreath. There is either no fin at all on the tail, or a low 

 one, which does not extend to the extremity of the tail, or a fin below only, 

 or one both above and below : therefore we can form three sub-genera ; — 



1. Trygon, (restricted). A fin on the tail, above and below. (H spj 



2. Hemitrygon, Nob. Fin of the upper margin of the tail wanting. — 

 r2sp.j 



3. Himantura. No fin on the tail. ( 6 sp.^ 



Pteroplatea, Nob. The Sting Rays, which are much broader than long, 

 with a tail shorter than the body, and teeth terminating in one or thre 

 points. (3 spj 



Taeniura, Nob. has no upper caudal fin, the inferior one extending to 

 the extremity of the tail. Teeth pointed, with an elliptical base. Mouth 

 undulated j the projecting parts of the upper jaw form a sharp edge on each 

 side. (1 sp. Tr. ornata, Gray and Hardw.) 



Hypolophus, Nob. Distinguished by its inferior caudal fin, which is ve- 

 ry high, and does not reach to the end of the tail. Teeth hexagonal, very 

 small in the middle of the upper jaw, large at the sides. (I sp. Raia ) 



Lastly, the Raia cruciata, Lacep. is the type of our genus, 



Urolophus, remarkable for a fin at the point of the tail. Teeth as in 

 Raia, bearing in the middle a wreath or point. (1 sp.J 



Another family has the tail of Trygon, but wants the sting. 

 To this belong two genera : — 



Anacanthus, Ehrenb. Tail without any fin. (1 sp.J And 



Urogymnus, Nob. having, on the under side of the tail, a low fin, which 

 does not reach to the extremity of the tail. (1 sp. Raia asperrima, Bl. Schn.) 



Myliobatis, Cuv. (Aetobatis, Bl. j Rhinoptera, Kuhl, and a new genus, 

 are put in one family, characterized by its large teeth, arranged as in a 

 pavement, or like mosaic work ; — by the' pectoral fins being separated from 

 the fins of the head; — by a fin upon the root of the tail, and a sting behind 

 this fin. 



* The genus Propleygia, Otto, is founded on a kind of monstrosity, which 

 is not seldom met with in Skates. 



