8 THE PLAGIOSTOMIA. 



marinus of Klein, later named Trygon aspera by Cuvier, 1817, and here 

 identified with Rata cent our a of Mitchill, 1815, and Trygon thalassia of 

 Miiller and Henle, 1841, from Columna. The name Trygon was applied 

 to this genus by Cuvier, 1817, from an unpublished work of Adanson, 1844 

 to 1845, Cours d'hist. nat., 2, p. 170. The genus Trygon of Cuvier, that 

 is the genus Dasybatus, contained species that are types of several different 

 genera. These having been removed, the genus, under the earlier name, 

 Dasybatus, is found to contain subgenera to which various names have been 

 applied. Riippell, 1828, in Atl. reise N. Afrika, p. 51, gave the name 

 Pastinachus to a subdivision containing two species, Trygon lymma 

 {Rata lymma Forsk., 1776) and Trygon sephen {Raia sephen Forsk., 1776) 

 characterized by a fin fold wholly or partly subtending the tail. Riippell, 

 1835, took the name Pastinachus, for a species wholly without fin folds, 

 D. uarnak. As he could not by accepted usage make such a change, the 

 name must be retained with at least one of the species originally included. 

 Miiller and Henle, 1837, took the species without traces of fin folds, D. 

 uarnak, for their division Himantura, and, disregarding Riippell's earliest 

 arrangement, took one species of Pastinachus, P. lymma for the type of 

 their genus Taeniura while the other, P. sephen, was placed as the type, 

 and only species, of a new genus, Hypolophus. The latter is not generically 

 distinct; its type remains in Dasybatus, the type of a subdivision under the 

 name originally bestowed by Riippell, 1828. The recognized sections of 

 Dasybatus are (1) Himanturus Miiller and Henle, 1837, without fin folds 

 or keel on the tail, (2) Pastinachus Riipp., 1828, with a fin fold below the 

 tail, equal Hemitrygon Miiller and Henle, 1838 and Hypolophus Miiller 

 and Henle, 1837, (3) Dasybatus with a keel above the tail and a fin fold 

 below, as in D. pastinacus, and (4) Amphotistius, the species of which have 

 fin folds on the tail both above and below, as in D. sahinus and D. kuhlii. 



Myliobatis. — Cuvier, 1817, founded this genus on Raia aquila of Linne, 1758, 

 a species not placed in Aetobatus by Blainville, 1816; thus the two genera 

 cannot be synonymous. 



Aetobatus. — Blainville, 1816, hsted eleven species. From these authors com- 

 monly have chosen Raia narinari Euph., 1790, as the type. Restricted to 

 A. narinari and its closest allies, there is no conflict with Myliobatis Cuv. 



Mobula. — Rafinesque, 1810, Ind. itt. Sic, p. 48, 61, founded this genus on i?aza 

 mobular Lacepede, 1798, Poiss., 1, p. 151. The type is that named Raia 

 mobular by Bonnaterre, 1788, Ichth., p. 5, with references to Duhamel's 



