322 DISCOVERY REPORTS 



Skogsberg (1920, p. 584) considered, like Miiller, that Claus was not justified in placing H. globosa in 

 the separate genus Halocypria, since the differences were of 'so slight a nature'. He had not then 

 studied H. globosa and when later (1946) he redescribed this species he revised his views somewhat. 

 He then considered that in many ways the species was intermediate between H. brevirostris and 

 Conchoecia. A definite decision on this question must be deferred until other species of the genus 

 have been redescribed, but in view of the small variation in the structure of the coxal gnathobase in 

 Conchoecia and the differences in other genera, it seems likely that Claus was justified in his opinion. 

 The two species should probably be placed in at least separate sub-genera, if not separate genera. 



Miiller (1906) described the interesting species Thaamatocypris echinata. In many ways this 

 resembles the halocyprid genera; in particular the mandible possesses a gnathobase on the basis as 

 well as on the coxa. The maxilla and first trunk-limb are similar to those of the halocyprids and bear 

 similar vibratory plates. Though its distal article differs from, the maxillule somewhat resembles, that of 

 Conchoecia ; there are, however, many differences, the most remarkable of which would appear to be 

 the absence of an antennal notch. This would seem to be related to the fact that though the antennal 

 shaft and exopod are similar to those of the halocyprids, the endopod also is well developed and has 

 a natatory function. In addition the antennule is distinctly segmented and is possibly natatory 

 (Skogsberg, 1920, p. 119). In relation to these differences Skogsberg discussed the stabilizing effect 

 of the spines on the carapace. It is also noteworthy that the caudal furca differs from that of the 

 halocyprids. It would be interesting to know if the mandible has a similar articulation to that of the 

 other halocyprids. Midler's figures (1906, pi. vi) indicate that there are many differences in the incisor 

 edges of the mandible, while the molar surface must be of quite different structure. In addition the 

 terminal setae of the mandibular palp are elongate and not claw-like. The figures and description give 

 no reference to any process on the coxa, which could represent the articular process of other halo- 

 cyprids. If such an articulation is absent, it would add further weight to the differences between the 

 Thaumatocypris and the other halocyprids. The impression is that Miiller was justified in placing his 

 species in a sub-family separate from that including the other Halocyprididae. 



COMPARISON OF HALOCYPRIDIDAE AND CYPRIDINIDAE 



Skogsberg (1920) compared the morphological details of the appendages of the Halocyprididae with 

 those of the Cypridinidae, but did not compare the whole animals from a functional viewpoint. 

 Graham Cannon (1931, 1933) has made such a comparison between the Cypridinidae and the Podo- 

 copa. A similar comparison with the Halocyprididae is of interest. 



An immediately obvious difference between Conchoecia and a cypridinid is the form of the carapace 

 and the antennal notch (Fig. 14). In the former group, the carapace is usually elongate with a straight 

 hinge-line and is very light and delicate ; in the latter it is generally rounded with a curved hinge-line 

 and is heavily calcified. The antennal notch of Conchoecia extends back very nearly parallel to the 

 hinge-line with a well-developed rostrum above. Behind the notch, the surface of the carapace is 

 hollowed to allow free backward swing of the antennal exopod. In the Cypridinidae the antennal 

 notch is narrower and usually slopes upward towards the hinge-line ; there is no prominent rostrum. 

 Associated with differences in the carapace there is a difference in posture of the animal. In a 

 typical cypridinid the main axis of the body slopes anteriorly upward much more markedly 

 than it does in Conchoecia. The ventral apodemes, which are similar in the two groups, indicate an 

 upward curvature of this axis much further forward in Conchoecia than in Cypridina. The nervous 

 system, also, extends further to the posterior in Conchoecia (cf. Claus, 1891, pi. 1, fig. 11 and Graham 

 Cannon, 1931, fig. 10B). The antennal shaft adds to the appearance of anterior uptilting in Cypridina. 



