all 
TANAIS VITTATUS. 127 
the base of the terminal setee. The lower antenne are 
shorter and more slender than the upper, apparently 
four-jointed, the second joint being short, the three 
others of nearly equal length, but gradually becoming 
more attenuated towards the tip. The foot-jaws resemble 
those of TJ. Dulongit (in our figure the dilated inner 
plate of the second joint is omitted, having been lost in 
dissection). The fore legs are very large, strong, smooth, 
and polished, the hand produced at its lower angle into 
a strong immovable finger, having a very small obtuse 
tubercle near its base and another beyond the middle, 
the intervening space being filled up by a thin portion 
of the edge. Several of the terminal pairs of legs are 
furnished with a strong sickle-shaped finger, having a 
tooth at a little distance beyond the middle of the inner 
edge, the space between it and the base being denticu- 
lated. In the individuals which we have examined the 
under-side of the body is not furnished with the incu- 
batory pouch, nor with the short appendages observed 
at the inner base of one or more pairs of the legs. In 
others, however, as represented by Rathke, the bilobed 
incubatory pouch is of large size, occupies the under 
surface of the intermediate segments of the body, and 
consists of very transparent membranes, allowing the 
eggs to be distinctly perceived from beneath; its posi- 
tion and appearance indicated in our woodcut being 
copied from Rathke’s figure. The most striking cha- 
racter of the species, however, consists in the very dense 
pencils or fascicles of long thin hairs with which the 
upper surface of the second and third segments of the 
tail are clothed, and which are set on at right angles to 
the body. The terminal segment of the tail is slightly 
notched in the middle of the under surface of its pos- 
terior margin, and is furnished at its sides with a pair 
