te 
PHRONIMA SEDENTARIA. 25 
short, terminating in a minute double point, and flanked on 
each side at the base with two little wing-like appendages, 
These are smooth and arcuated upon the upper margin, 
but straight and regularly pectinated along the lower. 
The next two pairs of legs are jong and simple; the 
succeeding pair are developed into the form of a perfect 
claw, each branch having a tubercle near the base on 
the inner edge, these tubercles being finely tuberculated ; 
the last two pairs of legs are short and simple. The 
natatory appendages are short, but have arobust peduncle. 
The caudal appendages resemble each other, but the 
penultimate pair are about half the length of the 
others. They consist of a long, slender peduncle and a 
couple of styliform branches. The middle tail-piece is 
very small, 
Dr. Pagenstecher, of Heidelberg, has published a very 
interesting anatomical and physiological memoir on this 
species in Wiegmann’s ‘ Archiv fir Naturgeschichte,” 
for 1861, in which he has made us acquainted with the 
early and intermediate states of the animal. In the 
earliest condition the antennz are very small, dilated, and 
jointless; the seven pairs of legs are of uniform size 
and shape, each consisting of seven joints, including the 
small basal joint by which it is attached to the body, and 
the very minute terminal hook. The joints of the tail 
are almost undeveloped, the whole tail being scarcely 
larger than the preceding segment. In the intermediate 
state the third and fourth pairs of legs are considerably 
elongated, and the fifth pair have become cheliferous.* 
The tail and its appendages have also acquired consi- 
* The progress of development in this genus offers a curious contrast to 
that of Brachyscelus crusculum as described by Spence Bate, ‘* Annals of 
Natural History” for July, 1861, in which the sixth pair of legs are cheliferous 
in the young stage, becoming simple in the adult. 
