SPH EROMIDA. 399 
are inserted close together, in the middle of the front of 
the head, and have a multiarticulate flagellum. The seg- 
ments of the body do not exhibit, when viewed dorsally, 
the epimera-like structure of the basal joints of the legs 
observable in the Idote:de. In some few species the first 
or the first two pairs of legs are subcheliform (as in the 
genus Ancimus) ; but the third pair are always simple. 
In the majority, all the legs are slender, and simply formed 
for walking, with a generally bifid terminal finger. The 
basal segments of the tail are more or less rudimentary, 
and in general soldered. together more or less completely, 
so as to form, apparently, only a single joint, which in 
many species is furnished with large tubercles or spines. 
The five pairs of branchial feet (pleopoda) are affixed 
obliquely on the underside of the large joint of the tail, 
which is deeply excavated for their reception. They are 
very delicate and membranous in their structure, the 
three anterior pairs being strongly ciliated on their 
apical and external edges; and the second pair, in the 
males, are furnished with an elongated slender-pointed 
style. The terminal pair of the tail-legs (uropoda) con- 
sist of two horizontal plates, of which the outer only 
is movable, the inner one being either occasionally 
obsolete, or soldered to the basal support. They are 
attached at the sides of the terminal joint near its 
anterior margin. 
Professor Milne Edwards has proposed a separate 
family (Spheromiens chelifers) for the reception of a re- 
markable new genus (Ancinus), upon a specimen of un- 
known locality contained in the British Museum, which 
has the first two pairs of legs terminated by large and 
strong hooks, and the body so flat as to be almost folia- 
ceous. The inner plate of the lateral appendages of the 
tail is wanting, whilst the outer is greatly elongated; but 
