TANAIS VITTATUS. 127 



the base of the terminal setae. The lower antennae 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 T. Dulongii (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 



