318 DESCRIPTIONS OF PARASITIC COPEPODA. 



lateral eoriiers well rouuded, the froat dorsal surface divided off as 

 shown i;ii fi<;. 1, and the dorsal groove reaching to near the hinder end 

 of the hood. The thickness through the hood is nearly equal to its 

 width, the region about the mouth being much exsert, and the base 

 of the head somewhat coustricted near where it joins the thorax. 



In dorsal view, the thorax is rather narrow in front and bilobed on 

 each side, the front lobes being very small, sometimes but faintly in- 

 dicated, and the posterior, which immediately follow them, quite large 

 and regularly rounded, the width of the thorax at this point being not 

 very much less than that of the abdomen. The larger lobes give origin 

 to the second pair of thoracic appendages. The abdomen is also divided 

 near the middle into two segments by a rather broad and shallow cqn- 

 strictiou, deepest and best defined at the sides, and indicated on the 

 dorsal surface by a very slight transverse depression. In contracted 

 si)ecimens this division is frequently more marked. The posterior seg- 

 ment is generally slightly longer and bro ider than the anterior, and its 

 length is about equal to the thickness through the abdomen. The pos- 

 tero-lateral prolongations of the hinder segment are rather short (a 

 little more than one-third the length of the segment), stout, and well 

 rounded at the extremities. In some cases they taper rapidly', while in 

 others they retain a more uniform width. The genital segment is small ; 

 the tail very small, elongate, rounded at the end, and with two minute 

 api)endages on the ventral side near the front, each tipped with a 

 single stout seta. 



The anterior antenuse are large, broad, flattenetl, but not as con- 

 spicuous as in Chondracanthus cottunculi, and consist of only a single 

 joint, although the setie at the outer end are borne upon a small, over- 

 lapping and elongate fold or lobe, as shown on pi. X, tigs. 2, 3. In speci- 

 mens normally preserved they stand almost entirely in advance of the 

 head, and reach nearly or quite to the lateral margins of the head; great- 

 est length about twice the greatest width ; the adjacent margins slightly 

 overlap[»ing. The front and inner margins are strongly convex; posterior 

 nuirgin straight or slightly concav^e, with a small, rounded prominence 

 or lobe near the inner end ; outer end abruptly narrowed, rounded, and 

 with several small setne. In contracted specimens these antenntie are 

 often drawn down to a greater or less extent over the ventral surface 

 of the head, thus appearing much less conspicuous dorsally. (See 

 plate VIII, figs. 4 and 5.) 



The second antennee or prehensile hooks are rigid, of a light horn 

 color, and arise from a rather complicated frame-work of the same con- 

 sistency, imbedded in the soft ventral surface of the head, close to the 

 front margin. They are strongly incurved near the end, and terminate 

 in a sharp point, but the lower two-thirds to three-fourths is nearly 

 straight. Their length, not including the incurved portion, is about 

 equal to the greatest width of the anterior antennae. 



