120 TANAIS. 
cylindrical joints and a rudimentary flagellum, which is, 
however, considerably elongated in some species, as in 
T. Edwardsii, where it is seven-jointed ; according, how- 
ever, to Fritz Miiller, the sexes differ in the structure 
of their antenne. A small auditory cavity exists in 
the first joint of the peduncle. These antenne are 
attenuated to the tip, which is furnished with a strong 
pencil of hairs. The lower antenne resemble the upper 
in direction and length, but they are more slender, and 
consist of a five-jointed peduncle, of which the first 
and third are short and ring-like, and the fifth is also 
terminated by a few hairs, within which is also a rudi- 
mentary flagellum. The mouth is well formed for biting. 
The upper lip is conical, resembling that of the Gammari, 
with a ridge along the medium line terminating in a 
produced point. The lower lip is formed of two ovate 
pieces fixed obliquely, united together at their extremity, 
leaving a triangular space between them, arising from 
a reversed triangular piece rounded at its base.* The 
mandibles are horny and elongate-triangular, terminated 
in a denticulated point rather incurved, with a deep 
impression and a movable denticulated tooth fixed be- 
neath the apex; towards the base on the inner edge, is 
a strong somewhat squared molar tooth, truncated, and 
having the entire edge of the truncated part notched 
for chewing: in the middle of the outer edge is a small 
tubercle emitting a short bristle, probably representing 
the mandibular palpus. The inner pair of maxille 
are strong, formed of a long, curved, sub-cylindrical 
outer portion, with the apex truncate and spinose, and 
a biarticulated inner division with the tip of the second 
* We believe this piece, represented. by Savigny as described above (and 
more nearly agreeing with the figure of the same organ in Gammarus than in 
Cymothoa), is identical with the piece described under the name of Under- 
leben by Kroyer (Tidssk. iv. 170). 
