108 Dr. F. Miiller on the Metamorphoses of the Prawns. 
small ridges and tubercles. At the base of the tooth, towards the | 
masticatory surface, there are several stiff bristles, beset with 
short spinules (fig. 7). The upper jaws are destitute of palpi. This 
appears to be a peculiarity in which all Zoée agree with Insects, 
and which is in this case doubly remarkable, because not only 
does the perfect animal possess mandibular palpi, but even the 
younger larvee have at this place biramose feet, from which the 
mandibles are produced., 
In the lower jaws (mazille, fig. 4 1v, v) we distinguish—1. the 
peduncle with projections on its inner side, which have almost the 
appearance of joints, and are beset with strong bristles, partly 
spimiform and partly toothed or plumose; 2. a multiarticulate 
apical portion (inner branch ?), which bears longer and more 
delicate bristles on its inside and at its apex; and 3. a small, 
elongated, lamelliform appendage (outer branch; fouet, Milne- 
Edwards, fig. 4a a), on the margin of which are placed a few 
delicate setee. In the first pair of maxille (1v) the peduncle has 
two long, and in the second pair (v) four shorter processes ; 
the apical portion has in the former three, and in the latter five 
joints. 
The footjaws (vt, vit) or macillipeds appear to assist but 
little in locomotion. They consist of a thick peduncle (thickest 
in the first pair), a long 4-5-joimted inner branch, and a shorter 
inarticulate outer branch. Besides the apical sete, there are 
bristles of various lengths upon the inner margin of the peduncle 
and of the inner branch, and also upon the outer margin of the 
outer branch. The first pair is longer and more powerful than 
the second. 
The two branches of the ¢adl project, separated by a semicir- 
cular notch, nearly at a right angle to each other; they appear 
to be rounded off at the apex, and twice acquire a new bristle on 
their inner margin, so that the number of these rises first to 
seven and then to eight on each branch. The oldest bristle 
continues to be recognizable by its greater length (0°4 mill.) ; 
the outermost bristle (the spine which is present even in the 
youngest Nauplius) continues to be distinguishable from the rest 
by its bemg smooth, whilst the others are rendered plumose by 
short spinules and longer hairs. 
The alimentary canal presents no peculiarity ; the anus, which 
is at first situated at the apex (PI. IV. fig. 3), afterwards moves 
forward on the ventral surface nearly to the middle of the last 
segment (fig. 6). The diver, of a yellowish colour, consists of 
three pairs of wide tubes (one pair anterior and superior, one 
pair lateral, and one pair posterior and inferior), and does not 
differ in its structure from that of other Zoée. 
The heart (fig. 3 h) occupies the usual position at the end of 
