16 G. 0. Sårs. 



The antennæ (see Pl. 2, fig. 4, Pl. 3, fig. 5), which 

 form the chief locornotory organs of the animal, originate 

 with a broad base from the sides of the head, in front of 

 the mandibles, and in the living animal are extended, together 

 with the anterior part of the head, from the shell in 

 front. As in other Limnadiids, they each consist of a thick, 

 muscular basal part, or scape, and of 2 slender, multiarticu- 

 late rami issuing from its tip. The scape forms at the base 

 behind, a slight elbow-shaped bend, to which some ciliated 

 setae are attached. Its outer, very flexible part is divided 

 into several short articulations followed by a somewhat 

 larger one, which is strongly spinous in front. Of the rami, 

 the anterior one is a little shorter than the posterior, which 

 is fully twice as long as the scape. Both rami are divided 

 into about 15 short, lamellar articulations, which carry an- 

 teriorly short spines, posteriorly slender natatory setæ. 



The oral parts consist of the labrum, the mandibles 

 and a single pair of maxillæ. 



The labrum (see PI. 2, fig. 5) has the form of an oblong, 

 somewhat curved, fleshy lobe, proceeding from the ventral 

 face of the head posteriorly. It terminates in a digitiform 

 tentacular process finely ciliated at the edges, and has above 

 it a thin vertical lamella, which inserts itself between the 

 maxillæ, when the labrum is bent in against the mouth. 



The mandibles (ibid.) are strong bow-like bodies extend- 

 ing on each side vertically from the cervical suture, and 

 each terminating in a strongly incurved masticatory part 

 which exhibits a finely fluted triturating surface. 



The maxillæ (fig. 8) are rather small, with the terminal, 

 movable lamella of rounded form and edged with a dense 

 fringe of delicate, incurved setæ, all finely ciliated and bi- 

 articulate. 



