86 



CARBONIFEROUS ENTOMOSTRACA. 



differs by the posterior elliptical rings of rugae being less truly horixontal, and by tbe 

 anterior rugae, after sloping upwards and outwards halfway up the valve, turning back on 

 themselves towards the sulcus, in the front half of the valve, and thus forming another 

 but smaller, and still more oblique elHpse of concentric lines. 



Length 6"25 ; height 3*5; thickness 3'5 mm. Proportions 25 : 14 -. 14. 



Fig. 26, taken from one of the black carapaces found in the Carboniferous Limestone 

 of Little Island, Cork, by Joseph Wright, Esq., F.G.S., shows all the features very 

 clearly, including the rugae and the coarsely reticulate pitting of the surface of the 

 valves. 



E. biconcentrica has also been found in the Carboniferous Limestone Series near 

 Carluke. 



The ornament of E. concentrica, and especially of E. biconcentrica, has some analogy 

 to that of the Silurian E. migrans (Barrande, ' Syst. Sil. Boheme,' vol. i, SuppL, 

 pp. 514 and 515, pi. xxiv, figs. 10 — 14), inasmuch as the last has longitudinal 

 wrinkles or riblets curving along the ventral edge, and turned back on themselves in the 

 upper part of each moiety of the valve. They make, however, two nearly equal 

 concentric triangular patterns (not always regular) instead of elliptical curves. The 

 rugae also seem to be coarser, and the valves are shorter and rounder, with semicircular 

 ventral, and deeply indented dorsal margin. 



Barrande's E. dimidiata (op. cit., p. 513) also has traces of somewhat similar but 

 very delicate riblets. 



A little thickening on the anterior edge of the sulcus is visible in M. Barrande's 

 figs. 11 and 13, and also in our drawing of E. Burrovii (fig. 21); and this may 

 represent the large tubercle in the Cyprellce and Cypridellce ; also that in our Entomis 

 obscura, in E. pelagica, Barr., and E. iuberosa, Jones, as well as the spine in E. aciculata 

 Jones. The last three are Silurian. 



There is a strong resemblance in the ornamentation of the Carboniferous Entomids 

 with that of some of the Devonian species, formerly known as " Cypridinse " (alluded 

 to also by M. Barrande, op. cit., p. 515). A reference to the 'Annals Nat. Hist.' for 

 September, 1879, p. 187, pi. ii, figs. 11 and 12, will show that the Devonian forms 

 there figured and described as Entomis gyrata (Richter) have longitudinal riblets bent 

 sharply on themselves at each extremity, and cut into two by the vertical sulcus so as 

 to leave a concentric group on each moiety of the valve. 



3. Entomis Burrovii. Sp. nov. Plate IV, figs. 21 a — c. 



Fig. 21 shows fully the characters and features of a fine Entomis from Settle, West 

 Yorkshire. This is a dark-grey left valve, nearly oblong, truncate behind, rounded in 



