230 DR. G. H. FOWLER— BISCATAN PLANKTON : 



thicker than the stem ; diminishing towards the apex, constricted and bent upwards 

 before tlie middle of its length ; carrying five or six long spines on its dorsal border, 

 numerous short spines on the proximal two-thirds of its ventral border. Antenna i. : 

 the principal bristle carries about 33 pairs of foliate appendages (as in anietra), back- 

 wardly directed, diverging widely when both rows are seen from above them ; in front 

 of them are three or four short upright spines. A small pad [Schwiele) occurs on the 

 proximal accessory bristle ; hairs of the terminal bristles, if present, exceedingly minute. 

 Antenna ii. with two central bristles on the inner limb, the one about two-thirds of 

 the length of the other : the basal bristles more widely apart than usual, the one very 

 long and slender, the other short and leaf -like. Hook-joint of the right side very strong, 

 curved at first through about 90°, then curved through a widely obtuse angle ; slightly 

 thickened terminally, ending in a spike ; a tooth on the proximal part. Hook-joint of 

 the left side long, bent through 90°, ending in a spike. 



Eemale (Mean, 3'30).^ — Shell elongate, of more triangular outline than in the male, 

 because beginning to taper further back. Shoulder-ridge less marked, postero-ventral 

 angle more sharply rounded than in the male. Postero-dorsal spines and rostrum as in 

 the male. Ventral border arcuate ; the greatest height behind the arcuation, thence 

 tapering sharply forward. Frontal organ : the stem projects for soine distance 

 beyond the first antenna. Terminal joint nearly completely segmented from the stem, 

 tapering slightly, d-ejiressed above, but not bent so much upwards as in the male. 

 Spines more numerous on the dorsal border than in the male, extending over more than 

 the proximal half. Antenna i. with a long dorsal bristle. Antenna ii. with two 

 hairless central bristles, the one about two-thirds the length of the other, and with a 

 long and a short basal bristle. The terminal bristles and tubes more or less beset with 

 fine spines proximally : the longest but one with fine spines nearly throughout its length ; 

 the longest slightly lanceolate. 



Stage III. 



Male (Mean, 2-16). — Shell much as in Stage II. (the right shell of fig. 8 has a 

 slightly more triangular appearance than the left of fig. 3, owing to the jirojecting 

 gland-papilla). Prontal organ unsegmented, spineless, the terminal part not much 

 thicker than the stem, ending in a blunt point. Antenna i. with the principal bristle 

 of female character*. Antenna ii. as in Stage IV. 



Female (Mean, 2-3). — Shell much as in Stage II., but rather less markedly tri- 

 angular. Frontal organ unsegmented, spineless, much as in the male of the same 

 stage. Antenna i. with a short doi-sal bristle (not shown in fig. 16). Antenna ii. as 

 in Stage II. 



Stage IV. 



Male. — A much broken specimen of 6 1"6 mm. was apparently referable to this : 

 the frontal organ and inner branch of antenna ii. have been figured. 



* This carried a straight dorsal bristle in one specimen, presumably as an abnormality; the same was occasionally 

 noted in males of other species. 



