NO. 1573. PARASITIC COPEPODS— WILSON. 433 



up of the males of other genera, and must wholly disappear as our 

 knowledge of these parasites becomes more complete. 



The thing to do, therefore, is not to refer the female to the genus 

 of the male, for the male has no genus, but to do exactly the reverse, 

 take the male out of this heterogeneous collection known as ^^Noga- 

 gus'' and place him in a valid genus to which the female belongs. 

 Hence, the question to determine is, to what genus does the female 

 described by Beneden belong ? 



Bassett-Smith suggests (1899, p. 459) that it is a species of Dysga- 

 mus, but unfortiuiately no female of this genus has ever been described, 

 so that we have no type with which to compare it. 



The Dysgamus male, as described by Steenstrup and Liitken, the 

 founders of the genus, is not a Nogaus form at all, but one in which 

 the first three segments of the thorax are all united with the head to 

 form the carapace, the fourth segment only being free. 



A furca is present, and the details of the appendages, especially 

 the swimming legs, are very difi'erent from what we find here. 



The female, when found, must belong to the Eurypho rinse, while 

 this female described by Beneden is evidently one of the Pandarinse. 

 Moreover it presents exactly the characters here given to the genus 

 Nesippus; the carapace is wider than long; the second and third 

 thorax segments are fused together and furnished with a single pair 

 of lateral lobes; the frontal plates are conspicuous; the genital seg- 

 ment is- elongated; the abdomen is short and one-jointed; the anal 

 laminee are relatively small, but armed with large setie; the swim- 

 ming legs are all l)iramose, the first three pairs are two-jointed, the 

 fourth pair one-jointed. 



This '' Nogagus," therefore, is really a female Nesippufi, and the 

 species must be called Nessipus angustatus A an Beneden, since it is 

 different from those heretofore described. 



Beneden made his third mistake in supposing that he had two 

 sexes; what he describes as a male is really not a Nogaus form, but a 

 young female, with the egg-strings as yet undeveloped (see p. 444). 

 The true male of this species is probably the form mentioned above, 

 which Beneden described as the male of Paridarus ajfinis. We have 

 alreatly shown that this was not a Paridarus but a Nesippus male; it 

 came from exactly the same locality, the Bay of Dakar, was collected 

 by the same man, M. Chevreux, and was sent to Beneden in the same 

 lot with the female specimens. 



Moreover it corresponds exactl}^ in bod}' form and in so much of 

 the anatomy as can be made out from Beneden's data. We may 

 conclude, therefore, 1, that the female of Beneden's Pandarus 

 affinis was a true Pandarus, and as such it has been included in the 

 key on page 394; 2, that what he described as the male of the same 

 Proc. N. M. vol. xxxiii— 07 28 



