nezo or rare Scottish Entomostraca. 211 



third pair with both branches three-jointed; fourth pair with 

 outer branch three-, inner branch two-jointed ; fifth pair 

 rudimentary. 



This genus has been provisionally instituted to include a 

 species closely related to Artotrogus, but from which it is at 

 once distinguished by the structure of the swimming-feet and 

 the rudimentary siphon. 



Parartotrogus Richardi^ sp. n. (PI. VII. figs. 1-11.) 



Length exclusive of tail-setse '5 millim. Seen from above 

 the first body- segment is subrhomboid, its greatest breadth 

 being equal to about one and an eighth times the length ; 

 forehead slightly produced, truncate. Anterior antennee 

 short, moderately stout, nine-jointed, the second joint con- 

 siderably longer than any of the others ; the formula shows 

 the relative length of the joints — 



12—20—6—5—6—10—12—13—14 

 1—2 _3— 4— 5— 6 — 7 — 8 — 9 ■ 



The antennse when bent back upon the body are scarcely half 

 the length of the first segment. Posterior antennee four- 

 jointed, the third joint nearly twice the length of the preceding 

 one and three times longer than the next ; armed with a strong 

 terminal claw, hooked at the apex ; a rudimentary one-jointed 

 secondary branch springs from the middle of the second joint. 

 Siphon very small. Mandibles small, stylet-shaped. Maxillae 

 small, with two one-jointed spiniferous branches, one branch 

 much smaller than the other. Anterior and posterior foot- 

 jaws nearly as in Artotrogus magniceps^ Brady. Both 

 branches of first pair of swimming-feet two-jointed, the last 

 joint of both branches (but especially of the inner branches) 

 dilated and bearing several plain setge ; (?) third and fourth 

 pairs as in Lichomolgus fucicolus^ Brady, but more slender and 

 with the marginal and termiilal spines broadly dagger-shaped ; 

 fifth pair small, bilobed, furnished with a few apical setse. 

 Ovisacs two, large. No maFps were observed. 



Remarks. Only three pairs of swimming-feet could be 

 observed, even after the moipt careful dissection of several 

 specimens ; it appeared to be the second pair that was 

 wanting, as a considerable hiatus existed between the first 

 pair and the next, much greater than between the fifth and 

 the preceding pair. 



This species was first known to us in 1889, having been 

 obtained in material dredged near Fidra Island, Firth of 

 Forth. Since that time it has been occasionally observed 



