TRIPAPHYLUS MUSTELI. 161 



viz. one pair of antennae and two pairs of feet ; the 

 posterior is much more narrow, and rounded, and 

 carries at the end two rounded tubercles which pro- 

 bably represent the fifth pair of feet ; the body may 

 also be divided into head, thorax, and abdomen. On 

 the sides of the cephalic portion we distinguish a 

 pair of setiferous antennas showing feeble indications 

 of articulation ; the mouth is terminal and fringed 

 with minute setas. The mandibles and maxillas are 

 somewhat rudimentary. The two pairs of maxillipeds 

 are comparatively well developed, and form prehen- 

 sile appendages similar to what is found in the males 

 of many of the sedentary female fish-parasites. 



The thorax is dilated (or bulging), smooth and 

 even on the surface; it carries two pairs of feet 

 singularly formed, and nearly as dilated and elongate 

 as the abdomen. The feet of both pairs are con- 

 solidated in all their length as the organs of adhesion 

 in the females of the Lerneopodians ; it is only at the 

 end that they are divided. The anterior pair is 

 biramose ; the outer ramus is two- jointed, and is ter- 

 minated by a double hook for clinging. The other 

 pair is longer; the outer ramus shows three articu- 

 lations terminated by two hooks, as in the outer ramus 

 of the preceding pair, but on the base of the hooks is 

 a small additional tooth which renders these organs of 

 adhesion more effective. 



It will be seen from the above description and the 

 drawing PI. XLV, fig. 6) that there are some of 

 the Lernaean males considerably removed from the 

 ordinary type. 



Habitat. Parasitic on the gills of the smooth hound, 

 Mustelus vulgaris (Sqnalus musielus). Irish Sea (A. 

 Scott). 



VOL. I. 11 



