246 DE- G- H. rOWLEE — BISCATAN PLANKTON : 



whicli makes nearly a right angle with the dorsal border ; postero-ventral angle rounded ; 

 ventral border sometimes slightly arcviate, generally straight, sloping downwards so that 

 the hio-hest point of the shell is well in front of the middle of the length. Prontal 

 oro-an unseo-mented, the future terminal joint thicker than the stem; its dorsal border 

 risino- a Little (sometimes sharply) at about half the length ; its ventral border convex and 

 with a few fine teeth in the male ; terminating acutely. Antenna i. with the principal 

 bristle of female character in both sexes ; no differentiation of the accessory bristles from 

 the sense-tubes in the male, no dorsal bristle in the female. Antenna ii. with two 

 central bristles on the inner branch, the one more than twice the length of the other and 

 provided with a few stout hairs. 



Stage V. (Mean + 0-5). 



Shell much as in Stage IV., but rather shorter for its height, and with the down- 

 ward slope of the ventral border more marked. Frontal organ and Antenna i. 

 much as in Stage IV. Antenna ii. with a single short stout central bristle carrying 

 a few short hairs. 



CoNCHCECiA PKOCERA, Muller. 

 ? = C. decipiens, Muller. 



(Plate 22. figs. 169-183.) 

 Only one sexual male stage was represented in the Biscayan collections, and this 

 aoreed with the form hitherto described as procera. But the presumption is that a 

 second (final) male form exists in this as in the larger species. It seems likely that this 

 is to be found in the species named decipiens by Miiller, which he himself (p. 72) at first 

 ranked as procera, and only separated from it later in his investigation. Procera occurred 

 at all but one of the nine ' Valdivia ' stations from which he records decipiens, and 

 there is nothing in his description of the latter to make its identification with procei^a 

 improbable. 



Stage II. 



Shell with the length more than twice the height, shoulder-ridge marked, postero- 

 dorsal angle rounded, posterior border convex ; no postero-ventral angle is perceptible on 

 the left side, but on the right side the posterior and ventral borders meet at the opening 

 of the asymmetrical gland as two distinct curves ; the opening is prominent, and is 

 placed further forward than is usual in other species. A small spine may or may not 

 be present on the right shell. 



Male (Mean, 1-11). — About twenty pairs of teeth on the principal bristle of antenna i. 

 are not uncommon. There are sometimes a few short hairs on the longer central bristle 



of antenna ii. 



Female (Mean, 1-16). — In figure 176 is drawn a slightly diff'erent type of antenna i. 

 from those drawn by Muller (xiv. 3 to 6) showing the " Albatross-bill " end which occurs 

 in cophopyga and hrachyaskos. 



