52 ZOOLOGY. 
able, very small, posteriorly rounded and convex, laterally acute, giving points of attachment 
to two inferior, transverse, and very slender pieces, situated close to the posterior margin of the 
sternal shield, to which system the anterior piece undoubtedly belongs. The fifth pair of legs 
is likewise articulated upon that segment. Upon the extremity of the posterior transverse piece 
just alluded to, is articulated a rudimentary caudal appendage, or so called oviferic leg. 
The sternal shield is subtriangular; its summit, which is directed forwards, being truncated. 
It is composed of four transverse pieces, soldered together, and corresponding to the anterior 
four pairs of legs. - It is a little longer than the cardial region above. 
The eyes, semiglobular in shape, are inserted upon a very short peduncle immediately beneath 
the base of the rostrum, and directed forwards. 
The inner antenne have a peduncle composed of three articles. The basal is globular, inserted 
immediately beneath the peduncle of the eye. The second article is the longest, very slender, 
subcompressed, slightly curved, implanted upon the inner edge of the first or basal, and pro- 
vided upon its inner margin with a row of setee. The third article is shaped like the second, 
more slender, and one third shorter: the antenna proper is about the length of the second 
article of the peduncle, compressed, tapering, consisting of eleven narrow articles, the inferior 
edge being provided with a double series of very short sete. A filiform, eight-jointed append- 
age, may be observed inserted at the upper and anterior margin of the third article of the 
peduncle, and s’ orter than the anterior proper. 
The external antenne, inserted upon the same transverse line as the inner, are slender, elon- 
gated, cylindrical, and tapering to a point, composed of narrow and somewhat irregular articles, 
upon a length of nearly one inch and a quarter. Their peduncle, about a quarter of an inch 
long, is composed of four articles, two of which might almost be considered as forming but an, 
irregular odd basal, at the upper and anterior margin of which a rudimentary processus may 
be observed. The two remaining articles are subcylindrical: the fourth is the longest. 
The inferior labia, or else anterior abdominal segment, on the sides of which the external 
jaw-legs articulate, is very small and bidentate. 
The external jaw-legs are pediform, provided internally with sete, and composed of six arti- 
cles besides the basal. Upon this, and exteriorly, is inserted the palpa, the first article of 
which is exceedingly small; the second slender, subcompressed, and elongated; the third, small 
and cylindrical, is followed by a lanceolated, thin blade surrounded with sete. When stretched 
out, the tip of the palpa extends to the base of the terminal article of the jaw-leg properly so 
called. The first article of the jaw-leg proper is the smallest of the six composing it; the 
second and third, subprismatic in shape, are the largest; the fourth, fifth, and sixth, are sub- 
depressed, the latter conical, and the three together equal in length to the second and third 
combined. 
The second pair of jaw-legs consists of the same number of parts as the first or external pair, 
viz: of a palpa and a mandible; both being composed of the same number of articles; its differ- 
ences consisting in a smaller and more slender form, and in the palpa being more elongated than 
the mandible, with its first article almost as long as the second. Sete occupy the same edges 
and surfaces. i 
The first mandible, or third pair of jaws, is composed of a triple foliaceous cochloid piece, sub- 
crenated upon its margin, each expansion being provided upon its base with a rudimentary 
palpa, and the external having in addition an elongated membranous expansion which extends 
towards the gills. 
Finally, the second or inner mandible (fourth pair of jaws) is an elongated and rigid piece, 
composed of three articles intimately soldered together; the third article being the most de- 
veloped of the three, and terminated by a subcircular and interiorly concave head, giving to the 
whole the form of a small dipper, at the upper and anterior part of which a small rudimentary 
palpa may be seen, inclined inwardly. 
