Note on the Family of Ifyliohatoids. 137 



MYLIOBATIS Dum. 



§ Holorhinus Gill. 

 Myliobatis Californicas Gill. 



Rhinoptera vespertilio Girard. 

 Holorhinus vespertilio Gill. 



This species has not the slightest affinity to Rhinoptera, as 

 may be at once perceived by reference to the figure published 

 by Girard (Boston Jour., N. EL, VI, 1857, p. 26). It only 

 difi'ers from the typical species of the genus by the narrower 

 median teeth — which are about three times as wide as long — 

 and by the wider rhomboid ventrals. 



The Myliobatis vespertilio Bleeker, having been named pre- 

 viously (1851), the present species cannot retain the specific 

 name originally conferred on it. 



AETOBATIS M. H. 

 JEtobatis laticeps Gill. 



The greatest width is rather more than twice as great as the distance 

 from the snout to the front of anus. The head is rather broad and 

 nearly equals the distance from the snout to the division between the 

 nasal lobes. The snout is obtusely angulated in front, and at its sides 

 is convex and scarcely angulated ; its width, at the line of the front of 

 the nostril, is as great as the distance from its point to the interlobular 

 nasal emargination. The rostro-frontal fontanelle is constricted at its 

 anterior third ; the interval between the crests of the anterior portion 

 enters about 2§ times in the interorbital area ; at the constriction, about 

 four times, and at the posterior portion, about 2§ times ; the posterior 

 portion gradually expands backwards and terminates with an oval con- 

 tour behind. The nasal lobes are about twice as long as wide, their 

 length externally exceeding half the length or breadth of the rostral 

 area. 



The dental plate has a triangular contour ; its anterior angle is 

 obtusely rounded. 



