84 FOSSIL ESTHERIiE. 



9. EsTHERiA ovATA, Lea, sp. Plate II, figs. 26 — 38. 



PosiuoNOMYA MINUTA (Bronn), W. B. Rogers. Proc. Acad. Nat. Sc. Pliilad., 1843, vol. i, 



p. 249; PosiDONiA, sp. ? Proc. Boston Soc. Nat. Hist., 

 1854, vol. Y, p. 14. 

 — (?), lAjell. Quart. Journ. Geol. Soc, 1847, vol. iii, p. 274, fig. 6. 



PosiDONiA OVATA, Lea. Proc. Acad. Nat. Sc. Philad, 1856, vol. viii, p. 77. 



— PARVA, Lea. Ibid. 



— ov.'lLIS, Emmons. Geol. Rep. North Carolina, 1856, p. 32.3, fig. W., 1 and 2 ; 



Amer. Geol., part VI, 1857, p. 40, fig. 12 ; Manual Geol., 2nd edit., 1860, 

 p. 191, fig. 166, 3. 



— MV hticosTA.-! A. E?nmons. Geol. Rep. N. Carolina, 1856, p. 337, fig. X ; Amer. 



Geol., part VI, 1857, p. 134, fig. 103; Manual of Geol., 2nd 

 edit., 1860, p. 191, fig. 166, 4. 



— TRIANGULARIS, .E'm»iows. Geol. Rep. N. Carolina, p. 338, fig. V ; Amer. Geol., 



part VI, p. 134, fig. 104. 



Inch. Inch. Inch. Inch. Inch. 



Height, y'g tV ••• less than -^ ... more than ^--3 ...more than ||- 



Length, ^^ -fl •■•••• » 1*2 ••■ less than -^^ ...less than ^2 



Proportion... 1 : 11 ... 1 : If 1 : li+ ^ • H+ 1 : 1| — 



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 con- 

 centric ridges are about fifteen in fig. 26 ; 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 

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

 which, owing to some peculiarity of growth, the ridges are too numerous to be very 

 distinct, and are unaccompanied with any ornament of the interspaces (figs. 29, 30). In 

 other specimens we find, besides blank surfaces (fig. 31), 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 struc- 

 ture. Figs. 33, 34, 35, and 36 are reticulate 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 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 pressure. Fig. 38 seems to show 

 narrow interspaces bounded by thick ridges and crossed by short, thick bars. 



