356 GEOLOGICAL SURVEY OF THE TERRITORIES. 



ESTHERIA OVATA JoneS. 



Posiclonomi/a minnta (Broun.) W. B. Rogers, Proc. Acad. Nat, Sci. Philad., 1843, vol. 



1, p. 249; Fosidonia, sp. ? Proc. Boston Soc. Nat. Hist., 1854, vol. 5, j). 14. 



?Lyell, Quart. Journ. Geol. Soc, 1847, vol. iii, p. 274, fig. 6. 

 Fosidonia ovata Lea, Proc. Acad. Nat. So. Philad., 1856, vol. 8, p. 77. 



parva, Lea, ibid. 

 P. ovalis Emmous Geol. Eep. North Carolina, 18.56, p. 323, fig. W, 1 and 2 ; Amer. 



Geol., part 9, 1857, p. 40, fig. 12; Manual Geol., 2d edit., 1860, p. 191, 166, 3. 

 P. multicostata Emmons, Geol. Eep. N Carolina, 1856, p. 337, fig. X; Amer. Geol., part 



6, 1857, p. 134, fig. 103; Manual of Geol,, 2d edit., i860, p. 191, fig. 166, 4. 

 F. triangularis, Emmons, Geol. Eep. N. Carolina, p. 338, fig. 5 ; Amer. Geol. part 6, p. 



134, fig. 104. 



Inch. Inch. Inch. Inch Inch. 



Height f -iV-. Less than -i%. .More than -f^.. .More than 21 



Length tV ^i t% Less than ^2-... Less than -^ 



Proportion 1:1J 1:1| l:lf + I:li4- 1:H — 



"Carapace A^alves broadly subovate, almost semicircular; the straight 

 dorsal line reaches across the valve, the extremities curving suddenly 

 downwards; the postero-dorsal angle being the sharper of the two. 

 The front and posterior margins are nearly equally rounded, but the 

 valve is usually deepest at the anterior third, in a line with the umbo ; 

 the well-curved ventral border being rather more oblique posteriorly 

 than anteriorly. The concentric ridges are about fifteen in fig. 2G, 

 about twenty-eight in fig. 27, and much more numerous in fig. 28. In 

 fig. 27 we see the gradual crowding of minor concentric ridges tov/ards 

 the ventral border in an adult specimen, and in fig. 28 we have an in- 

 dividual in which, owing to some peculiarity of growth, the ridges are 

 too numerous to be very distinct, and are unaccompanied with any orna 

 ment of the interspaces (figs. 29, 30). In other specimens we find, besides 

 blank surfaces (fig. 37), modifications of a reticulate ornament on the 

 interspaces (figs. 32, 36), with occasionally a barred or transversely 

 wrinkled pattern (figs. 37, 38). Fig. 31 is a set of narrow interspaces, 

 smooth and without ornament. Fig. 32 shows how a smooth surface 

 may mask the reticulate structure. Figs. 33, 34, 35, and 36 are reticu- 

 late interspaces, the meshes being of various sizes and arranged either 

 longitudinally, diagonally, or vertically. In the first case the walls of 

 the meshes would strengthen if not give rise to minor concentric strice ; 

 in the last case they may give rise to the bar-ornament, such as is seen 

 in fig. 37. The obliquity of the meshes in fig. 35 may be due to pres- 

 sure. Fig. 38 seems to show narrow interspaces bonneted by thick 

 ridges and crossed by short thick bars. 



"For most of these illustrations we have had recourse to specimens 

 from Pennsylvania, Eichmond, and Dan River (from Prof. W. B. Eogers' 

 collection), which evidently belong to the species. These specimens 

 are — 



1. From Pennsylvania. Black shale. Estherise excessively crowded 

 in horizontal layers. 



2. From Prince Edward, near Eichmond, Ya. Black shale, with con- 

 choidal fracture, fine-grained. Estherise tolerably well preserved, but 

 crumpled. 



3. From Dan Eiver, North Carolina. Black, laminated shale, ob- 

 liquely crushed. Estherite very thin." 



Leaia, gen. nov. 



"I have proposed the above name as a generic denomination for cer- 

 tain peculiar, quadrate, bivalved carapaces, occurring in the Coal- 



