256 ZOOLOGY.. 



able, very small, i^osteriorly rounded and convex, laterally acute, giving points of attacliment 

 to two inferior, transverse, and very slender pieces, situated close to tlie jJosterior margin of the 

 sternal shield, to which system the anterior piece undoubtedly belongs. The fifth pair of legs 

 is likewise articulated xipon that segment. Ui)on 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 foTir 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 antennce have a peduncle composed of three articles. Tlie basal is globular, inserted 

 immediately beneath the peduncle of the eye. The second article is the longest, very slender, 

 subcompressed, slightly curved, imi^lanted upon the inner edge of the first or basal, and pro- 

 vided upon its inner margin with a row of setaj. The third article is shaped like the second, 

 more slender, and one third shorter : the antenna j^roper 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 sette. A filiform, eight-jointed append- 

 age, may be observed inserted at the upper and anterior margin of the third article of the 

 peduncle, and shorter than the anterior proper. 



The external antennas, inserted upon the same transverse line as the inner, are slender, elon- 

 gated, cylindrical, and tajjering 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 ujiper 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 ijediform, provided internally with setse, 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 setaj. When stretched 

 out, the tip of the palpa extends to the base of the terminal article of the jaw-leg projjerly 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, fifths 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. Setfe occupy the same edges 

 and surfaces. 



^hQ 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 expajision 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. 



