8 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.64. 



similar to those in Pandarus male; frontal plates prominent, sepa- 

 rated by a deep central sinus. Free segments without dorsal plates, 

 all of the same width which is equal to that of the genital segment. 

 Second segment with a pair of postero-lateral lobes, extending diag- 

 onally outward and backward; fourth segment with a lateral knob 

 on either side, nearer the anterior margin. Genital segment with 

 knob-like processes at anterior corners and wide rounded lobes at the 

 posterior corners. Abdomen two-jointed, joints equal. Swimming 

 legs all biramose, rami two-jointed. Maxillipeds with stout ter- 

 minal claw, shutting against two corrugated knobs on basal joint. 



PARAPANDARUS NODOSUS, new species. 



Plate 2, figs. 19-24 ; plate 3. 



Host and record of specimens. — Twenty females and ten males of 

 this new genus and species were taken from the gills of a large ham- 

 merhead shark, Sphyma zygaena^ at Woods Hole, July 5, 1911. All 

 were full grown and the females each bore egg strings. Both sexes 

 were securely fastened to the gill arches by their powerful second 

 antennae and maxillipeds. This will be noted as one important 

 difference between the present genus and Pandarus^ the latter being 

 always an external parasite on the fins or skin. 



A single female has been selected as the type of the new species 

 and has been given Cat. No. 54139, U.S.N.M. The remaining speci- 

 mens become paratypes with Cat. No. 54140, U.S.N.M. 



Specific characters of female. — To the generic characters already 

 given the following may be added. The width of the carapace across 

 its posterior margin is to its length as 8 to 5 ; the posterior cornerjs 

 are bluntly rounded and point straight outward ; the posterior mar- 

 gin is nearly straight and has no trace of teeth, so common m 

 Pandarus. On either lateral margin, a short distance in front of 

 the posterior corner is a notch representing the division between 

 the head and the first thoracic segment. If a line be drawn from this 

 notch diagonally inward and backward to the center of the posterior 

 margin, the triangular corner of the carapace outside of and behind 

 the line will represent one dorsal plate of the first thoracic segment. 

 In specimens which have become swollen by the preservative this 

 first plate is often inclined upward at an angle with the rest of the 

 carapace, and is thus still further differentiated. The dorsal plates 

 of the second, third, and fourth thoracic segments are attached to 

 the dorsal surface of their respective segments diagonally, and pro- 

 ject outward and backward in broadly rounded curves. The com- 

 bined width of the two plates forming each pair is about equal to that 

 of the carapace. The first pair do not quite touch each other on the 

 midline and a triangular portion of the second segment comes to an 



