1885.] 



CLADOCGRA. 



n. 



Description of the Species, with Observations on Vital 

 Phenomena. 



Family: — Sididæ. 



1. Diaphanosoma excisum, n. sp. 



(Pl. 2). 



Specific Character. — Female: — General form of body 

 very similar to that in D. brachyurum. Head obtusely truncate 

 anteriorly, without any distinct sinus beneath the eye; dorsal 

 margin faintly arched. Carapace oblong, truncate posteriorly, 

 with upper angle almost a right one, valves inflected in the 

 middle and wide-open posteriorly, having a well-marked angu- 

 lar emargination at the junction of the ventral and posterior 

 margins. Eye comparatively large, with a light, brownish pig- 

 ment. Antennæ, when reflexed, not reaching posterior margin 

 of carapace. Tail of usual structure, caudal setæ exceedingly 

 elongate. Body highly pellucid, with a faint yellowish tinge» 

 Length of full-grown female reaching 1,30 mm. 



Re marks. — This Australian species exhibits in its general 

 habitus a very striking resemblance to the well-known northern 

 form, D. brachyurum, Liévin, but has also a certain affinity to 

 the closely allied species, B. brandtianum, Fischer, and would 

 seem, as it were, to occupy an intermediate rank between the two. 

 From both, however, it may be readily distinguished by the 

 peculiar angular emargination of the valves posteriorly, a cha- 



