248 DE. G. H. FOAVLEE — BISCATATST PLANKTON : 



CONCHCECIA RHYNCHENA, Muller. 



(Plate 23. figs. 188-204.) 



The specimens showed only one male stage with secondary sexual characters : it is 

 possible that Tcanipta or tylocla may be the oldest stage of this species. However this 

 may be, the rhynchena stage is liere regarded as Stage II. 



Stage II. 



The shells were a little less elongate than in Miiller's figure (xxvi. 21), but the 

 characters of antenna i. in the male left no doubt of the identification. In both sexes 

 the opening of the right asymmetrical gland projects markedly beyond the shell-outline 

 (figs. 190, 195) ; the left lateral gland is found at the pronounced angle between the 

 posterior and the ventral borders. The following notes are supplemental to Miiller's 

 description. 



Male (Mean, 2'28). — Antenna i. The armature {Bldttchen) of the principal bristle 

 was observed to amount to about 53 pairs of foliate teeth. The pad {Scliwiele) on the 

 proximal accessory bristle appeared to be formed by an increase in the diameter of the 

 appendage, strengthened by chitinous three-quarter-rings ; it is opposite to the distal 

 half of the armature of the principal bristle : distal to it, are about eight pairs of stout 

 teeth, the pairs set widely apart from one another. On the distal accessory bristle are 

 20-40 pairs of stouter teeth, approximately opposite to the pad. Antenna ii. : there 

 are two central and two basal bristles,- the shorter in each case is about one-half the 

 length of the other ; all are apparently hairless. 



Pemale (Mean, 2'47). — The spines on the Frontal organ w^ere rather stouter and 

 fewer than in Miiller's figure (xxvi. 17 «) J ^^^t it agreed with this in general contoiu*. 

 The terminal joint is markedly segmented from the stem. I have added drawings of 

 slightly sharper and blunter specimens, but all show the same general type and 

 spination. Antenna ii. : the central bristles as in the male, no basal bristles. 



As some difficulty was found at first in separating this from ? /orica^a, subjoined are the conspicuous 

 differences between them. 



Rhynchena $ . Posterior border nearly straight, nearly perpendicular to the dorsal angle, no 

 arcuation of the ventral border, marked sculpture at the anterior end of the shell. Postero-dorsal 

 glands present, frontal organ segmented from the stem, opening of the right asymmetrical gland 

 markedly projecting. 



Loricafa ? . Posterior border convex, extending behind the perpendicular from the dorsal border, 

 ventral border arcuate, sculpture of the anterior end of the shell inconspicuous. No postero-dorsal 

 glands, frontal organ incompletely segmented from the stem, opening of the right asymmetrical gland 

 conspicuous but not markedly projecting beyond the shell-outline. 



Stage III. 



Male (Mean observed* 1-75, probable + 1-55). — Shell rather less elongate than in 

 the subsequent Stage II., posterior border slightly convex, ojiening of right asymmetrical 

 gland slightly projecting as before. (The rostrum in fig. 190 is not quite in profile, 

 and looks shorter than it really is.) Frontal organ unsegmented, the future terminal 



* Only two specimens of this stage were seen. 



