442 PROCEEDINGS OF THE NATIONAL MVSEUM. ^ vol. xxxiii. 



The larger of the two forms he found to be males, identical with 

 I^each's Nogaus latreillii; the smaller ones were females, and he con- 

 sidered them as the females of the same species. 



The only reasons actually given for this opinion were that the two 

 forms were found on the same fish and were of the same color. 



The statement was also made that a detailed examination con- 

 firmed this view, but no details were given. 



This assumption of the identity of the two sexes led Kroyer to the 

 further declaration (p. 173) that Dana's Nogagus validus and Specil- 

 ligus curticaudis, which were taken together upon one fish, are prob- 

 ably the two sexes of the same species. 



Nogagus tenax (Steenstrup and Liitken, 1861) and Nogagus gracilis 

 (Burmeister, 1832) he also regarded as females of the same genus. 



In fact, Kroyer regarded the two groups into which Steenstrup and 

 Liitken had divided their Nogagus species as made up, the one group 

 of males and the other of females. 



A careful examination of Kroyer's description, and especially of his 

 excellent figures, makes it reasonably certain that the smaller forms 

 which he called the females of Nogagus latreillii, and. which were stated 

 to be immature, are really young females of the genus Nesippus. If 

 his figures be compared with figure 205 of the present paper, which is 

 certainly an immature Nesippus, it will be found that they are so 

 similar as to leave little doubt that they belong to the same genus. 



Furthermore, there are in the collection of the U. S. National 

 Museum several lots of specimens obtained by the steamer Albatross 

 of the Bureau of Fisheries. Each lot includes the species obtained 

 from a single fish, and in three instances these embrace specimens of 

 Nogaus latreillii and Nesippus alatus. 



The two have been obtained together on the same fish by the 

 author also on several occasions. 



As to Dana's two species, Nogagus validus and Specilligus curti- 

 caudis, whicli have been personally examined and are described on 

 pages 397 and 434, they are both certainly males, and therefore could 

 not very well be the two sexes'of the same species. This is also true 

 of all the Nogaus species described by Steenstrup and Liitken which 

 have come under the author's observation. They are all males and 

 are clearly so described by those authors. 



As the search for a Nogaus female progressed it became more and 

 more evident that t^lie forms grouped under the genus name ' ' Nogagus " 

 were in reality the males of several different genera. 



As early as 1861 Steenstrup and Liitken, in speaking of the Panda- 

 rinae, after deploring the fact that both sexes were known of but a 

 single species in the entire subfamily, ask the question, "May not the 

 forms included in the genus Nogagus be the true males of those females 

 belonging to the genera Dinemura, Phyllophorus, Pandarus, Ganglio- 



