NO. 5.] ACCOUNT OF THE SPECIES. 101 



of the anterior division of the body, and rather densely setiferous, especially 

 in their proximal part; right prehensile antenna in male with the dilated 

 part, preceding the geniculation, composed of only 4 articulations, the last of 

 which has anteriorly a deep, semilunar emargination defined by 2 spiniform 

 projections, of which the proximal is rather strong, terminal part rather 

 longer and 5-articulate, 1st joint fusiform, and projecting at the end ante- 

 riorly to a small hamiform prominence. 3rd and 4th pairs of legs with a 

 deflexed spine at the outer corner of the 2nd basal joint, especially large in 

 the 3rd pair, apical spine of outer ramus very strong and coarsely denticulate 

 outside. Last pair of legs in female with the terminal joint almost twice the 

 length of the other 2 combined, narrow linear in form, and carrying at the 

 tip 2 unequal spines, the inner one the larger and somewhat incurved. Right 

 leg of this pair in male with the 3rd joint irregularly oval in form, exhibiting 

 outside 2 angular prominences, terminal claw abruptly curved in its outer part 

 and carrying at some distance from the base a small spine; left leg likewise 

 with a small spine outside the terminal spine. Length of adult female 1"10 mm., 

 of male 1'05 mm. 



Remarks. This form, at first sight, somewhat resembles the above- 

 described new species of Heterochceta (H. compacta), exhibiting a similar 

 short and compact form of body. It is, however, in reality very different 

 as regards the structural details, and is also of very inferior size. 



Description of the Female. 



The length of the body in fully grown specimens does not exceed 

 1"10 mm., and this form is accordingly of rather small size. 



The general form of the body (see PI. XXX, figs. 1 & 2) is very short 

 and stout, so far greatly contrasting with the preceding species, Metridia 

 longa, which is one of the most slender of known Calanoids. The anterior 

 division is rather tumid and, seen dorsally (fig. 1), exhibits a rather regular 

 oval form, with the greatest width almost equalling half the length, and 

 occurring in the middle. The anterior extremity appears obtusely rounded, 

 and the posterior is of about the same width, and slightly emarginated in the 

 middle, with the lateral corners rounded off. The cephalic segment is well 

 defined, whereas the last 2 pedigerous segments are imperfectly separated. 



