NO. 1573. PARASITIC COPEPODS— WILSON. 441 



With reference to his first statement, in spite of the fact that the 

 tliorax segments are separate and free, only the first one being joined 

 witli the head, nevertheless he places the genus under the "Caligidce," 

 and not under the "Pandaridas," where it would legitimate!}^ belong. 

 To judge from his tabular key to the various genera this location of 

 Nogaus was based upon the fact that none of the species (which he 

 now increases to three) possesses any tlorsal plates upon the free 

 thorax. 



But again he forgets that these three species are made up exclu- 

 sively of males, upon whose free thorax there would naturally be no 

 dorsal plates, while the genera which he placed under the Pandaridee 

 are made up just as exclusively of females, who are the usual plate- 

 bearers. A little reflection also would show that this absence of dorsal 

 plates is more than overbalanced by the freedom of the thorax seg- 

 ments, and particularly by the structure and position of the mouth- 

 parts. 



These latter Milne Edwards entirely ignores, when even a cursory 

 examination would have shown that they are like those found in 

 Pandarus and allied genera, and considerably dift'erent from those of 

 Caligus and its near relatives. 



The genus being thus founded exclusively upon the characters of 

 the male sex, there has been a constant eft'ort to discover, if possible, 

 a female of some of the species, in order that the genus diagnosis might 

 be completed. 



Gerstaecker published in 1853 the first account of a Nogaus female, 

 which he called Nogagus productus. In discussing the synonymy he 

 makes Miiller's Oaligus productus, Otto's Caligus paradoxus, antl 

 Nordmann's Binoculus sexsetaceus synonyms of his Nogagus, and claims 

 that the latter name must stand by priority. 



jNliiller's Caligus produclus has been proved to l)e a Dinemalura, the 

 genus established for it in 1829 by Latreille, while Otto's Caligus 

 paradoxus was made the type of the genus Demoleus by Heller in 1S65. 

 Nordmann's Binoculus becomes a synonym of this latter genus. 

 Gerstaecker thus made two mistakes, fifst in supposing that Miiller's 

 female and Otto's male were the two sexes of the same species, and, 

 second, in assuming that Otto's male belonged to the same genus as 

 Nogaus latreillii, Leach's original t^'pe. These mistakes render his 

 paper of no value so far as the present genus is concerned, for the 

 female which he presents is not a Nogaus at all, but a Dinematura. 



The second attempt at finding a Nogaus female was made by Krover 

 in 1803. lie described (p. 168) several specimens of two kinds of 

 these ])arasites which had been secured from the outside surface of a 

 large Carcharias taken in the open Atlantic. 



