REPORT ON THE COPEPODA. 49 



Heterochceta spinifrons, Claus (PL XIII. figs. 1-13). 



Heterochceta spinifrons, Claus, Die frei lebenden Copepoden, p. 182, pi. xxxii. figs. 8, 9, 14, 16. 



Length, one-sixth of an inch (4*2 mm.). Cephalothorax slender, tapering to each 

 extremity (fig. 1), rostrum short, stout and bluntly pointed, not furcate. Anterior 

 antennas (figs. 1, 2) about as long as the body, slender; the base (in spirit specimens) 

 thrown boldly forward from the front of the head, and then taking a sudden bend 

 backwards ; sparingly provided with very short marginal setse, except near the 

 base, where they are longer and more thickly set ; apical joint rather short, its terminal 

 setse 1 not much longer than those of the other joints; in the male (fig. 3) the hinge 

 joint forms a scarcely perceptible indentation, and there are no marginal spines or 

 serratures. The inner branch of the posterior antenna (fig. 4) has four (? three) small 

 median joints, and is nearly equal in size to the outer branch. The mandible (fig. 5) has 

 four curved apical teeth, the two central teeth bi- or tri-furcate, the outermost tooth is, 

 as it were, soldered to the side of the basal plate, its base forming a rectangular projec- 

 tion, and between it and the other teeth there is a wide gap. The maxilla (fig. 6) is long 

 and slender, digitiform, has five or six stout apical setse, a quadrate basal plate, which is 

 marginally setose, and only one short tri-setose branch. The marginal setae of the 

 anterior foot-jaws (fig. 7) are very strong, and the last two are closely pectinated with 

 short fine setae on their inner margins ; at the apex of the limb is a tuft of about 

 six slender setse, about half as long as the larger claws. The posterior foot-jaws 

 (fig. 8) are like those of Calanus, but the basal joint bears one short spine, and an 

 excessively long and strong flexuous seta. All the branches of the swimming feet, both 

 external and internal, are three- jointed, the marginal spines are short, sharp and slender ; 

 the outer branch of the third pair (fig. 9) is, however, much dilated, and has a series of 

 very short claw-like terminal spines. The fifth pair in the male (fig. 10) are only slightly 

 different on the two sides ; the inner branches are two-jointed, ending in a brush of six 

 stout plumose setse; the outer branches end in long, slender claws, that of the right side 

 having two large digitiform processes on the inner margins of the first and third joints ; 

 in the female the fifth pair are alike on both sides (fig. 11), and differ little from the first 

 and second pairs, except that the median joint of each outer branch bears on its inner 

 margin a strong divaricate and slightly curved spine, which is as long as the third joint, 

 and in the natural position of the limb crosses its fellow of the opposite side. The first 

 abdominal somite in the impregnated female (fig. 12) is very large and tumid, the 

 receptaculum seminis (?) forming a large rounded prominence on its anterior aspect ; in 

 the male the abdominal joints are nearly equal in size. The caudal stylets are about 



1 These setae are scarcely long enough in the plate, and in fig. 1 the number of antennal joints is given 

 incorrectly. The figure (10) illustrating the fifth pair of feet of the male, though representing rightly the specimen 

 from which it was drawn, differs considerably from the same organs in other examples ; probably, however, the discre- 

 pancies are characteristic of the various ages of the specimens. 



(ZOOL. OHALL. EXP. — PART XXIII. 1883,) Z 7 



