MARINE ISOrODA OF NEW ENGLAND, ETC. 385 



liave tlieir first two segments large and flattened, and wedge-sliaped in 

 front ; of these the basal segment is quadrate in outline, as seen from 

 above, and nearly as broad as long; it closely a])i)roaches its fellow of 

 the opposite side in front, but is separated from it behind by a median 

 process of the head ; the second segment is triangular in outline, as seen 

 from above, with the apex of the triangle extending beyond the origin 

 of the third slender cylindrical segment, which is followed by a tapering 

 flagellum of about a dozen segments. The antennae when reflexed 

 extent! beyond the first thoracic segment and have the first two seg- 

 ments short and compressed, the third somewhat longer, the fourth 

 and fifth longer and nearly cylindrical, followed by a taiiering flagellum 

 about as long as the i^eduncle and composed of fifteen to twenty seg- 

 ments. The maxillipeds have a short triangular external lamella and 

 a five-jointed paljDus, of which the first segment is short aud transverse; 

 the second is triangular and bears, on its inner apex, a few slender 

 hooked spines ; the third segment is broad and flattened, with the inner 

 margin short, and armed with about three robust hooked spines ; the 

 fourth segment is flattened and transverse and armed along its inner 

 margin with about six similar spines ; while the fifth segment is small, 

 sub-oval, and armed with much more slender curved spines. The outer 

 maxillae are provided with curved spines at the apex much like those of 

 the maxillipeds. The inner maxillce are rod-like and terminate in sharp 

 somewhat curved spines placed close together. The mandibles support 

 a slender palpus of three segments, of which the middle one is much the 

 longest, and the last is robust and sickle-shaped, with a comb of short 

 spines along the inner curve. This segment lies, in the ordinary posi- 

 tion, just at the base of the antenna of the same side. 



The first thoracic segment is, at its anterior margin, scarcely broader 

 than the head, but expands rapidly backward. It is excavated in front 

 for the eyes, which project somewhat beyond the j)osterior margin of the 

 head. The second, third, and fourth thoracic segments are each a little 

 shorter than the first; the fifth and sixth are somewhat longer; the 

 seventh is shorter than the sixth. The epimera of the first thoracic seg- 

 ment are not separated by suture, but in the second aud following seg- 

 ments they are so separated, and, especially on the anterior segments, 

 marked with two oblique depressed lines. The epimera of the second, 

 third, and fourth segments are rounded or truncate behind, but in the 

 posterior segments they become acute and extend beyond the angles of 

 the segments to which they are attached. The iirst three pairs of legs 

 are short and armed with strong hooked dactyli. The propodal seg- 

 ments are also curved, and the carpus is short in the first pair but 

 somewhat longer in the second and third pairs. The merus is almost 

 crescent-shaped in the first pair of legs, its horns embracing the carpus 

 above and below, but it becomes more elongated in the succeeding pairs; 

 in aU three pairs its inferior margin is armed with a few short, stout 

 spines. The foirrth and succeeding pairs of legs are of quite a different 

 25 F 



