Fossil JSniomosfraoa from South America. 291 



with rounded and smooth edges, Fig. 3d ; thinner and smaller lower 

 down on the valve. 



The interstitial spaces are broad on the upper or dorsal moiety of 

 the valves, more and more closely set below, as in other adult EsthericB. 

 The ornament in the broad interspaces consists of small vertical 

 bars, or barrolets, slightly sinuous (Figs. 3d, e), and occasionally 

 branching and anastomosing to some extent. Towards the free 

 margin, in the narrower intervals, the barrolets become shortened, 

 and merge into a wavy and crenulate pattern (Figs, of, g). 



Two carapaces, " L. 304." 1. Long, 7-0 mm. ; high, 4-0 mm. ; 

 thick, 2-6 mm. 2. Long, 5-7 mm. ; high, 3-6 mm. ; thick, 3'0 mm. 

 Ovate-oblong, anteriorly short. From shale in a cutting on the Bahia 

 and San Francisco Kail road, 12-13 kilometres from Bahia, on the sea- 

 side, between Periperl and Olaria; together with some small Molluscs 

 — Anodonta Hartii, White, A. Mawsoni, White, A., sp., and Area, sp. 

 There are also other specimens, more or less flattened and de- 

 composed, in sandy shales and clay from cuttings at Pitanga, Pojuca, 

 and elsewhere. 



With regard to the ornamentation of this species, two recent 

 forms, SJstheria donaciformis, Baird,^ and £. similis, Baird,^ have 

 a bar-ornament in the interstices, of much the same character as 

 that in Figs. 3d-g, though not so regularly parallel. The valves, 

 however, do not correspond with ours in shape. 



Among fossil forms M elliplica, Dunker, and JiJ. subquadrata, 

 Sowerby, are characterized by the ornament of vertical bars between 

 the concentric ridges, much like those of E. Maivsoni. The shape, 

 however, of the valves in these Purbeckian forms ^ differs from that 

 of the Brazilian species under notice. There is evidence of a similar 

 ornament in some fragments of JEstheria from the Triassic or Ebgetio 

 coal-shales of Dan Eiver, North Carolina.* An analogous pattern is 

 present on the shells of some bivalved Mollusca, as Gorhis, etc. 



(5*) EsTHBRiA Mawsoni, sp. nov., variety or female form. 

 PLATE XI, Figs. 4-6. 



Ovate-oblong, umbo near the anterior end, in the front fourth 

 of the dorsal edge ; postero-dorsal angle more or less distinct ; 

 hinge-line straight between these two points, and equal to more 

 than half the length of the valve. The front and hind margins 

 have a steep curve, and are more equal than in E. Maiosoni, Fig. 3a. 

 But the postei'ior moiety of the carapace is rather smaller than the 

 anterior ; its edge having a somewhat smaller curve than the broad, 

 almost semicircular, curvature of the front end. 



This form differs from E. Maiosoni (described above) in being 

 nearly oblong in side-view ; the front edge curving steeply below 

 the umbo ; and the posterior not being contracted. The difference 



^ Proc. Zool. Soc, Annulosa, 1849, p. 89, pi. xi, fig. 5. 



2 Ibid., 1849, p. 90, pi. xi, fig. 7 ; and 1860, p. 188. 



3 " Monogr. Foss. Esth.,'" 1862, p. 103, etc., pi. iii, fi^s. 18-29 ; and Geological 

 Magaz-ne, 1890, p. 389, PL XII, Figs. 1, 2. " 



* "Monogr. Foss. Esth.,'" 1862, p. 189, etc., pi. ii, fig. 37; and Geological 

 Magazine, 1890, p. 387. 



