238 DK. G. H. rOAVLER— BISCATAN PLAXKTON: 



jmirs of minute teeth, set at about their own length from one another, followed 

 jn'oxinially by 15-20 pairs of similar teeth which are spaced more widely apart. 

 Antenna ii. as drawn by Miillcr (xx. 20, 21) : but the long hairs of the longer central 

 bristle are often missing (? dropped off) ; the shortei* bristle may carry a few short hairs. 

 Of the basal bristles, the one is rather longer than the other (the foreshortening in 

 camera drawings is ajit to mislead). 



Stage III. 



Female (Mean, 1'07). — Sliell practically indistinguishable from that of magna 

 Stage III., except for the lateral glands. Frontal organ of the same general type as 

 in Stage I., but less swollen, unsegmcnted, projecting far beyond the antenna. 

 Antenna i. Avith a hairless dorsal bristle. Antenna ii. with the central bristles as in 

 Stage I., but smaller. No basal bristles. 



Male (Mean, I'OS). — Shell practically indistinguishable from that of magna 

 Stage III., except for the lateral glands. Frontal organ resembling that of the female 

 Stage I., except that it shows no segmentation, and carries fewer and shorter spines. 

 Antenna i. with the three flagella clearly differentiated, the secondary a little more 

 than lialf the length of the principal. Armature of female character. Antenna ii. 

 without hooks; the central bristles as in female Stage I., but smaller. No basal 

 bristles. 



Stage IV. 



Male (Mean, 0'7). — Shell as in Stage II., but slightly higher in front of the arcuation 

 than behind it. Frontal organ swollen terminally, unsegmeuted, still bearing a 

 terminal spike. 



Female of this stage not observed. 



CoNCHCECTA IMBRICATA (Brady pars), Miiller. 

 (Plate 20. figs. 110-121.) 



Four stages were recognised in this species, of which only the oldest showed secondary 

 sexual characters in the male. From the analogy of other forms, I have no doubt that 

 a yet larger stage exists, and is to be found in deep water. 



Miiller records (p. 118) the lengths of S'O to 3-5 for females, 25 to 30 for males. 

 Measurements of his figure (xxviii. 1) show that he included rostrum and posterior spine 

 in the " length," and that his specimens corresponded to my Stage II., m ith means 

 of 2-31 S , 2-01 d . 



Stage II. 



Female (Mean, 2-34).— Shell agreeing \Aith that described and figured by Miillcr 

 (xxxviii. 1). Frontal organ sometimes rather more curved than in Miiller's xxxviii. 

 fig. 3, beset thickly with stout spines on tlie proximal fifth of its dorsal border and 

 proximalhalf of its ventral border. Antcnnai. with hairless dorsal bristle. Antenna ii.: 



