232 ON A LARÜE PENELLA-SPECIES. 



recognizable. The apical joint bears five short setae and 

 is moreover provided in the left antenna with a long 

 bristle; the basal joint is furnished with a row of several 

 stout setae. The posterior antennae consist of a short and 

 broad basal joint and the claw-shaped terminal one; they 

 agree in all regards with those of P. varians, figured by 

 Steenstrup and Lütken ^). In the middle-line between the 

 antennae a spot of black pigment indicates the place of 

 the unpaired eye. At the ventral side of the body the four 

 pairs of swimming feet are recognizable (fig. 3). The two 

 anterior pairs of them, lying close behind each other, are 

 situated nearly in the same line with the base of the arm- 

 like processes ; the third pair however does not follow 

 directly but is separated from the preceding one by a 

 distance of Vj^ mm., as is also the case with the fourth 

 pair. The two feet of the last-named pair are separated by 

 a distance twice as large as that between the feet of the 

 preceding pairs. P. crassicornis also has the pairs of 

 swimming feet situated on a certain distance from each 

 other ; nevertheless they seem to be arranged on an other 

 manner as in our species; in P. sagitta, varians and exo- 

 coeti the pairs of swimming feet appear to be placed 

 closely behind each other. The basal joints of both ante- 

 rior pairs are trapezoidal, those of the two posterior pairs 

 more triangularly shaped ; they have all in their middle 

 an irregular spot of dark-brown pigment. The first pair 

 of feet is furnished with single-jointed branches of a 

 roundish shape and only the right one of them bears two 

 branches, whereas the left foot has lost its outer branch ; 

 the basal joint bears a bristle at the exterior and the 

 interior side of the branches. The second pair has both 

 feet single-branched, the outer branch being lost and sub- 

 stituted by a spine. Of the third pair only the right foot 

 is furnished with a two-jointed branch; its distal joint 

 bears six long setae, the terminal part of which however 



1) loc. cit. pi. XIV, tig. 32. 



Notes from tlie Leyden Museum, "S'^ol. XXVI. 



