Ostraeodous and Phyllopodous Tribes. 77 



(De Koninck) has a most interestingly sculptured surface, each 

 valve being sculptured with concentric elliptical lines, like the 

 minute plicae or ridges of the skin on the inside of the human 

 finger-top. In E. hiconcentrica, Jones, each moiety of the valve 

 has this concentric ridging.* E. Koninckiana and E. Bur- 

 rovii, Jones and Kirk by, have the ridging coarser, more open and 

 vertical, that is, transverse to the valves, except on the ventral 

 region, where it is nearly parallel with the margin. The former 

 has fewer of the transverse riblets than the latter species ; both 

 have oblong outlines, and so also has E. ohscura, Jones and Kii'kby, 

 which is smooth or faintly reticulate. All of these belong to the 

 Mountain Limestone. Several Entomides, formerly termed Cypri- 

 dinse, occur in and characterize the " Cypridinen-Schiefer " of the 

 Devonian series ; several are known in the Silurian strata of Bo- 

 hemia, according to M. Barrande, and there are a few in the same 

 rocks in Scotland, especially the little E. aciculcda, Jones, from the 

 Pentland Hills, which has the subcentral tubercle produced as a 

 sharp spine. t 



Part IV. — Cyprid^ and Cytherid^. 



Among the Palaeozoic Bivalved Entomostraca occur many that 

 are indistinguishable, by means of their carapace-valves, from some 

 members of the CypridseX and Cytheridse.^ In the Coal-measures 

 we meet with valves like those of Candona ; and in many Carboni- 

 ferous shales and limestones Bairdia || is recognizable by its peculiar 

 triangular and apiculate valves, one overlapping the other, as well 

 also in the Permian Limestones in abundance, and even in Silurian 

 Limestones (Kildare). There are many Ostraeodous valves in the 

 Palaeozoic rocks ^ comparable with Cy there,** or some of the allied 

 genera ; and hosts of them occur in the Carboniferous strata. 

 Thlipsura ft was doubtless a closely related form, but is pinched in 

 posteriorly. CarboniaXX has the simple form of an oblong Cythere, 

 but shows the sunken lucid spots of the Leperditiadse.^ 



Part V. — -Phyllopoda. 



Other truly bivalved Entomostraca found in the older strata 

 belong to the Phyllopoda, such as Estheria \\ || and Leaia,^'^ for 

 which the reader is referred to my Monograph of the fossil Estheriae, 

 Palaeontograph. Society, 1862, and to the ' Greol. Mag.,' vol. vii., 

 p. 219. Estheria lives now, and there is little difference between 



* See Plate LXI., Fig. 13, p. 185, vol. iv. 



t See ' Ann. N. H.,' loc. cit., p. 416. J Vol. iv., p. 186. § P. 187. 



II Plate LXI., Fig. 1, p. 185, vol. iv. t P. 186. 



** Plate LXI., Fig. 3, loc. cit. ft Plate LXI., Fig. 2, p. 185. 



XX Plate LXI., Fig. 2, p. 185. §§ ' Geol. Mag.,' vol. vii., p. 218. 



nil Plate LXI., Figs. 23 and 24, and p. 185, vol. iv. IK Fig. 22. 



