FISHES MYLIOBATIDAE RHINOPTERA VESPERTILIO. 375 



are truly specific. For the present printed documents alone have served as standard to the few 

 comparative hints which have been attempted with an allied species of a more southern clime. 



HHINOPTERA VESPERTILIO, Grd 



SPEC. CHAR. Cephalic region equal to the rest of the body. Snout sub-elliptical upon its periphery instead of being 

 notched. Eyes prominent, and raised above the surface of the head. Transverse diameter of body more than twice its 

 length. Tail very slender and tapering. Above purplish blue or slate-colored ; beneath dull olivaceous. 



S.Rhinoptera vespertilio, GED. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 137 ; and, in Bost. Jour. Nat. Hist. VI, 1857. 

 Plate xxvi. 



This species is closely allied to H. javanica, from which it differs by the shape or outline of 

 the head, which is semicircular anteriorly, very slightly emarginated instead of being deeply 

 notched or concave, and by the lateral extremities of the pectoral fins which are less pointed. 

 The ventrals, on the other hand, are broader or more expanded. 



The specimen before us measures nineteen inches and a half from the extremity of the snout 

 to the tip of the tail ; six inches and three-quarters being the length of the body end head 

 together. The width from the tip of one pectoral fin to the other is twelve inches. 



The cephalic region is as long as the rest of the body ; its anterior outline, as already stated, 

 is rounded, and but very slightly emarginated, The eyes are quite prominent, and somewhat 

 raised above the surface of the head. The lips are fringed and the edge of the maxillar 

 membrane scalloped. The branchial apertures, five pairs in number, are transversely elongated 

 and disposed upon an open curve. 



There is a small dorsal fin situated posteriorly to the ventrals upon the anterior portion of 

 the tail, and followed by a lanceolated, horizontally flattened spine, serrated upon its edges. 

 The tail is very attenuated, flagelliform, tapering into a filliform extremity. 



The color above is of a purplish blue or of a slate tint, lighter towards the periphery than 

 upon the dorsal region ; beneath dull olivaceous. 



List of specimens. 



