458 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxiii. 



second maxillipeds have a short, curved claw and corrugated knobs; 

 the rami of the first three pairs of legs are two-jointed, of the fourth 

 pair one-jointed. 



This locates the species in the genus Perissopus, and on comparing 

 it with Heller's Nogagus cselehs and Nogagus elongatus, the three are 

 seen to be so nearly alike that it even seems prol)able they are but 

 variations of the same species. At all events they are very closely 

 related forms of the same genus. 



NOGAGUS SPINACII-ACHANTIAS Hesse. 



Nogagus spinacii-achantias Hesse, 1883, p. 1, pi. iv, figs. 1-7. 

 Pandarvs spinacii-achantias Hesse, 1883, p. 10, pi. vi, fig. 9. 



This species was described as a female by Ilesse, and was based 

 upon several specimens obtained from the head of a Spinax achantias; 

 the male was said to be unknown. We have already given Hesse's 

 reason for considering these specimens females (see p. 335). There 

 can be no doubt that they are really males, but almost no dependence 

 can be placed upon the figures and description given by Hesse. 

 For example, in the dorsal view the second legs have a three-jointed 

 exopod, while the endopod is not visible; in an enlarged figure of 

 the same legs they are represented with a three-jointed endopod and 

 a two-jointed exopod, while in the ventral view both rami are dis- 

 tinctly two-jointed. The text says nothing whatever about these 

 legs. 



In the face of these and many other similar discrepancies it would 

 seem almost hopeless to attempt to locate the species. 



But Hesse is at least consistent, and after a time we can learn 

 what to expect and can make rational allowances. 



A comparison of the figures and description he has given of the 

 present species and of a new Pandarus, found upon the same fish, 

 and named similarly Pandarus spinacii achantias, leaves not much 

 doubt that they are the male and female of the same species. 



First the relative sizes are correct, 5 or 6 mm. for the Nogaus and 

 6 or 7 mm. for the Pandaihis. 



In the second place, the new Pandarus is evidentl}" located cor- 

 rectly, as is sliown by the number and arrangement of the dorsal 

 plates and by the appendages. Hesse, however, gives it but three 

 pairs of swimming legs, describing in place of the first pair what 

 he calls — 



Appareil de fixation, qui est place transversalement a la base du bouclier cephalique 

 et represente par un tige qui emet, de chaque cote, des appendices recourbes ainsi 

 que de petits crocs, destines a sasir et accrocher les objets et est termine par une 

 longue griffe qui contourne une ventouse cupuliforme placee a I'extremite externe 

 du bouclier cephalothoracique. 



