THE OSTRACODA. 237 



the longer, which carries stout short liairs, is nearly twice the length of the shorter, 

 ■which carries comparatively few flue hairs. 



Only one well-in-cscrvcd specimen was ol)servecl, with a length of 2-5 mm. (3i.</, 

 750-500 fm.). A poorly preserved specimen of 2-1 mm. may also he referable to this 

 species (23a, 1000-750 fm.). 



Male (Mean, ±2-]).— Shell elongate, with a well-marked shoulder-ridge. Posterior 

 border nearly straight, and nearly at right angles to the dorsal border ; postero-vcntral 

 angle not marked ; ventral border slightly arcuate, tlic shell about as high in front of 

 the arcuation as behind it. Lateral glands conspicuous, and there is a collection of 

 long gland-cells on the ventral border of the left shell behind the arcuation (compare 

 Miiller's figure xx. 2). Prontal organ with the terminal joint very thick jiroximaily, 

 constricted about the middle of its length, expanding again to a rounded end. 

 Antenna i. with an armature showing about 66 teeth in profile view (it was not possible 

 to make ovit how many of these 66 were in pairs) ; the teeth are very small, closely set, 

 and as figured by Miiller (xx. d<), except that they appeared to be more sharply pointed. 

 Antenna ii. as drawn by Miiller (xx. 7, 9) : there is one long fine basal bristle with 

 fine hairs, and one very short bristle ; the longer of the two central bristles carries 

 short stout hairs distally as well as the long setse proximally. 



A single specimen, 2"3 mm. in length, was taken in the non- comparable haul 36 I 

 (350-0 fm.). 



Stage II. {hyalophyllmn stage). 



Female (Mean, 1'58). — Shell markedly resembling tiiat ol' magna at Stage 11., but 

 the posterior border is more sharply rounded, and on the ventral border the shell is 

 slightly higher behind than in front of the arcviation ; consequently the shell tapers 

 more anteriorly. Erontal organ and Antenna i. as drawn by Miiller (xx. 23, 24): 

 the tei'minal joint of the frontal organ has the dorsal and ventral borders less parallel 

 than in magna ; it swells gradually from the base towards the tip (not suddenly as in 

 pafckleidata) ; at the tip it is suddenly reduced to a sharp spine. The small spines on 

 the organ are more numerous than in magna, and are more concentrated anteriorly and 

 ventrally. The dorsal bristle of antenna i. carries numerous very fine hairs ; in pro- 

 portion to the diameter of the bristle they are larger than magna Stage II., but arc 

 almost equally difficult to see. Antenna ii. with the bristles much as in magna. 



Male (Mean, 1"50). — Shell much as in magna Stage II., but less arcuate and with 

 somewhat stronger shoulder-ridge. Ventral border very slightly arcuate, rising an- 

 teriorly sooner than in magna ; shell about as high in front of- the arcuation as behind 

 it. The lateral glands are often very difficult to see, both in male and female ; one 

 seldom finds more indication of them than the three little j)oints shown in tig. 97. 

 Frontal organ with the terminal joint curved as in magna,hw\, not so much constricted 

 in the middle (fig. 91) ; both ends nearly of the same thickness. Antenna i. : the 

 principal flagellum is a little longer than the two secondary flagella. The armature is 

 very difficult to make out, the teeth being, as a rule, hardly longer than those on the 

 principal flagellum of the female in many species. It appears to consist of about 22 



40* 



