564 NEW SPECIES OF PARASITIC COPEPODS. 



the iiosterior margiu. In alcoholic specimens the shape chauges more 

 or less, the greatest width frequently occurring farther forward. The 

 cephalothorax is distinctly marked off from the remainder of the body, 

 tliough closely adjoining and overlapping it. 



Back of the cephalothorax the body is elongate, with indications, 

 more or less distinct, of four segments, but the posterior limitations of 

 the thorax proper with respect to the dorsal shield are dithcult to de- 

 termine. Two general divisions of this portion of the body may be 

 recognized from above. The anterior division which composes slightly 

 less than one-half its entire length, is nearly square in outline, slightly 

 wider than long, of nearly uniform width throughout or enlarging some- 

 what posteriorly, and with Avell rounded corners. It is considerably 

 wider than the cephalothorax and than the third division of the body 

 •\dilch follows it. Near the middle it is slightly indented on the sides, 

 but iu alcoholic specimens it is also seen to be marked by a furrow 

 across the back, which is generally faint near the median line, but 

 deeper midway between the middle and the sides and often appearing 

 there like an elongate l)it, which stops short of the margin. 



The posterior division (the third of the entire body) is much narrower 

 than the preceding one, from the hinder margiu of which it originates 

 abruptly, as shown iu Fig. 2, PI. XXXI. It is elongate-ovate in outline, 

 with indented sides ; broadest anteriorly, about one-third longer than 

 the second division, and about two-thirds as long as wide, except when 

 contracted iu alcohol. That portion of it in advance of the lateral in- 

 dentations, being much thickened and giving origin directly to the fourth 

 pair of feet, should probably bo regarded as the fourth thoracic segment, 

 while thehinderpartalonecan properly bedesignated as thedorsal shield. 

 In alcoholic specimens, the fourth thoracic segment is separated from the 

 third by a dorsal furrow similar to that between the second and third 

 segments, but less distinct across the median line, and with the lateral 

 pits shorter, rounder, and deeper. The dorsal shield is subovate in 

 outline and rouuded at the posterior end, but is often narrower than 

 represented in the general figure (Fig. 2, PI. XXXI). It is very thin, del- 

 icate, flexible, and translucent, almost transparent in living specimens. 

 The cephalothorax and thorax are both strongly arched dorsally. 

 The former is moderately thick, the sides curving round to form a nar- 

 row elongate lobe or cheek on each side of the lower surface, reaching 

 well up to the a[)pendages. The thorax is nnn;h thickened, the ventral 

 surface of the first (more properly second) segment being concave be- 

 tween two lateral, elongate, raised folds. 



The thoracic feet of the third pair are very large, prominent, hood- 

 shaped, and project far out on each side of the body, as shown in both the 

 dorsal and ventral views represented on Plate XXXI, Figs. 1, 2. Each 

 consists of a large, strongly recurved lobe, attached along the inner 

 margin, presenting a convex surface anteriorly, with the lateral mar- 

 gins curved and subparallel, and the inclosed space opening obliquely 



