THE OSTEACODA. 231 



Female (Mean 1'42). — Shell much less triaagular than in the later stages, owing to 

 the ventral border being now slightly convex instead of arcuate. Spines, papillae, and 

 rostra as before, but rather shorter. Frontal organ still very long, unsegmented, 

 terminal part only slightly thicker than the stem ; ending bluntly, spineless. Antenna i. 

 without dorsal bristle. Antenna ii. Avith central bristles as in Stage III. ; no basal 

 bristles. 



CONCHCECIA BRACHYASKOS, Miiller, 



(Plate 16. figs. 20-29.) 



The specimens were xmfortunately too few to allow of the successive stages being 

 determined mathematically ; but at least two male stages, and possibly three female 

 stages, were recognizable : figures are given to help future observers. The shell of the 

 only male of "9 mm. was unfortunately damaged before being drawn ; it appeared, 

 however, closely to resemble the larger specimens. 



In addition to Miiller's description (p. 70) it may be noted that the older shells 

 generally carried a small spine, like that of procera. In the female, the frontal organ 

 was generally curved downwards more than in Miiller's figures (xiv. 7, 8). In the male, 

 the teeth of the armature of the principal bristle of the first antenna (fig. 21) seemed 

 rather more curved than in his drawing (xiv. 14). There were fifteen pairs of these 

 teeth more or less opposite to one another, followed by four single teeth proximally. 

 These differences were presumably within the limits of individual variation. 



CoNCHCECIA CTJRTA, Lubbock. 

 = C. stigmatica, Miiller. 



(Plate 17. figs. 30-54.) 



The special difiiculties presented by the shape and size of this species, which tend to 

 obscure the successive stages, are mentioned in detail on pp. 259, 260. In the male. 

 Stages I. and II. (the stages with secondary sexual characters) are pretty clear ; the earlier 

 stages are guesswork. In the female, the successive stages are little differentiated 

 morphologically and are by no means clear. I should not have dared to associate 

 stigmatica with the oldest stage of curta if the necessary confirmation by analogy had not 

 been available from larger species, in which one is on more certain ground ; but a careful 

 comparison of the figures with the similar succession in other forms will, I think, leave 

 no doubt of the correctness of the determination. The only point in which the succession 

 differs from that observed in the other species lies in the reduction of the number of 

 " teeth " on the principal bristle of antenna i. in the male ; they are, however, quite 

 rudimentary and inefficient, as compared with other species, at the previous " curta 

 stage ; " this being so, their further reduction at the " stigmatica stage " would seem to 

 suggest that they are being abandoned. 



It may be said that I have included two separate species under curta, and it is certainly 

 possible; but the possibility has been steadily borne in mind, and I have found myself 

 unable to split the species. Unfortunately the measurements of the older specimens 

 are too few to give any clue, and arc themselves somewhat chaotic. A large series of 

 older specimens is needed to set the species on a proper footing. 



