120 FOSSIL ESTHERF/E. 



Notes on the Beyrichia; and Cypridce associated with the Fossil Eslheriee. 



Occurring with Esthcrice, in deposits of different ages, both Palaeozoic and Meso- 

 zoic, are several small Bivalved Entomostracans, belonging, for the most part, to the 

 Lophyropoda j Tribe, Cyproidea ; Family, Cyprida. 1 A few other Entomostraca are 

 associated with some of the Palaeozoic Estheria ; and these belong probably to the 

 Phyllopoda ; Tribe, Limn ad 'io idea ; Family, Lejjerditida? 



As it is highly desirable to get as much information as possible respecting the 

 habitats of fossil Estheria, I determined not to neglect the associated Entomostracan 

 remains ; and have, therefore, figured them in PI. V, and will proceed to describe them : 

 but, with our present knowledge of them and their alliances, they throw but little 

 additional light on the subject. In fact, it is difficult to assign most of them to their 

 sub-families and genera, so similar are the carapaces of some generically distinct 

 Cypridce. 



1. Betrichia subarcuata, spec. nov. PL V, figs. 16, 17. 



Length, -W inch. Height, -^ inch. 



Carapace-valves elongate-reniform, the length nearly double the height (or breadth) ; 

 indented at the middle of the dorsal border by a short, transverse notch, reaching about 

 one fourth across the valve, and by another still slighter notch at rather less than half-way 

 between the larger notch and the anterior (?) end of the valve. The surface is delicately 

 reticular, with minute hexagonal pits (fig. 17). 



This Beyrichia feebly represents the well-lobcd Silurian forms of this genus : it is 

 very closely allied to B. arcuata, Bean, sp. ('Mag. Nat. Hist.' 1836, vol. ix, p. 377, 

 fig. 55). Indeed it may ultimately prove to be a variety of this species, which is very 

 common in the Coal-measures. B. subarcuata occurs with Estheria tenella in the Upper 

 Coal-measures at Astley, Lancashire (see page 32) ; and, if this species had the same 

 habits as the older Beyrichia, it speaks of marine conditions ; at all events we may regard 

 it as at least having a brackish habitat. 



1 See the Synopsis of the Crustacea, at p. 10. 



- This is the grouping which I have proposed for Beyrichia and its allies ('Annals Nat. Hist.,' Feb., 

 1856, p. 99), the carapace alone being considered. 



