356 GEOLOGICAL SURVEY OF THE TERRITORIES. 
ESTHERIA OVATA Jones. 
Posidonomya minuta (Bronn.) W. B. Rogers, Proc. Acad. Nat. Sci. Philad., 1843, vol. 
1, p. 249; Posidonia, sp.? Proc. Boston Soc. Nat. Hist., 1854, vol. 5, p. 14. 
? Lyell, Quart. Journ. Geol. Soc., 1847, vol. tii, p. 274, fig. 6. 
Posidonia ovata Lea, Proc. Acad. Nat. Se. Philad., 1856, vol. 8, p. 77. 
parva, Lea, ibid. 
P. ovalis Emmons Geol. Rep. North Carolina, 1856, p. 323, fig. W, 1 and 2; Amer. 
Geol., part 9, 1857, p. 40, fig. 12; Manual Geol., 2d edit., 18 ‘60, p- 191, 166, 3. 
P. multicostata Emmons, Geol. Rep. ‘N Carolina, 1856, p. 337, fig. xe Amer. Geol. part 
6, 1857, p. 134, fig. 103; Manual of Geol., 2d ‘edit. 1860, p. 191, fig. 166, 4 
Je triangulari is, "Emmons, “Geol. Rep. N. Carolina, p- 338, fic. 55. "Amer. Geol. eae p- 
134, fig. 104. 
Inch. 
Inch. Toch. Inch Inch. 
Height ee rs. “+ gee pee aa jls-. Less than 5%;..More than ~;.--More than 23 
2 Tz 
Geneth i 22e le Te eee eee es aS are jy--..Less than +3;... Lessthan 4 3% 
Proportion. sees koka eerie Meera ne iene une ate uk Len ae Lig ss 
“ Carapace valves 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. 26, 
about twenty-eight in fig. 27,and much more numerous in fig. 25. In 
fig. 27 we see the gradual crowding of minor concentric ridges towards 
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, 30), with occasionally a barred or transversely 
wrinkled pattern (figs. 37, 38). Tig. 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 
Jongitudinally, diagonally, or vertically. In the first case the walls of 
the meshes would strengthen if not give rise to minor concentrie striae ; 
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. 
“Kor most of these illustrations we have had recourse to specimens 
from Pennsylvania, Richmond, and Dan River (from Prof. W. B. Rogers’ 
collection), which evidently belong to the species. These specimens 
are— 
1. From Pennsylvania. Black shale. Estheriz excessively crowded 
in horizontal layers. 
2. From Prince Edward, near Richmond, Va. Black shale, with con- 
choidal fracture, fine-grained. Hstherize tolerably well preserved, but 
crumpled. 
3. From Dan River, North Carolina. Black, laminated shale, ob- 
liquely crushed. Estheriz very thin.” 
LEATA, gen. nov. 
“‘T have proposed the above name as a generic denomination for cer- 
tain peculiar, quadrate, bivalved carapaces, occurring in the Coal- 
a a ae 
