SKENIDIUM—ORTHIS. 143 
VIL. Family.—Stroppuomenipa, King, 1846. 
1. Genus.—Sxenipium, Hall, 1860. 
1. Skenrpium AREOLA, Quenstedt, sp. Pl. XVII, figs. 7, 8. 
21854. Ontuis PLICATELLA, Schnur. Paleontographica, vol. iii, p. 219, pl. xxxviii, 
figs. 4 a—e. 
? 1869. —  ueEpipus, Hall. Pal. N. Y., vol. iv, pt. 2, p. 46, pl. vi, figs. La—f 
1871. — AREOLA, Quenstedt. Petref. Deutsch., Band ii, p. 589, pl. lvii, fig. 27. 
1882. Skenrpium aREOLA, Davidson. Brit. Foss. Brach., vol. v, pt. 1, p. 49, pl. 
iii, figs. 11—14. 
1885. —_ _— Maurer, Abhandl. Grossh. Hessisch. Geol. Landes., 
vol. i, pt. 2, p. 141, pl. v, figs. 12—13 6. 
1892. as — Hall. Pal. N. Y., vol. viii, pt. 1, p. 243, pl. vii a, fig. 43. 
Locality.—There are sixteen specimens in my Collection, from Lummaton, 
chiefly detached valves. 
Size.-—A dorsal valve measures 11 mm. wide. 
Remarks.—The specimen figured by Davidson is smaller, and has fewer and 
more prominent and unequal ribs than the shell as figured by German authors ; 
but some of my specimens vary in the opposite direction, and, indeed, the 
difference is so great that it is possible that the English fossils may include two 
species or varieties. My larger specimens, besides the variation in ribbing, seem 
to have rather a lower and smaller beak. Some of these specimens so nearly 
resemble Orthis plicatella, Schnur, that there is little doubt of their identity, 
but it is not so certain whether these agree specifically with Quenstedt’s species. 
Orthis lepidus, Hall, seems to differ only in having rather finer and more equal 
ribs than the English specimens of the same size, and may perhaps be nothing 
more than a dwarfed variety. 
2. Genus.—Ortuis, Dalman, 1828. 
1. Orruis striatoLa, Schlotheim, sp. 
18138. TEREBRATULITES STRIATULUS, Schlotheim. Leonhard’s Min. Taschenbuch, 
vol. vii, pt. 1, pl. i, fig. 6. 
1867. OrrHis striatuLA, Davidson. Brit. Foss. Brach., vol. iii, pt. 6, p. 87, pl. 
xvii, figs. 4—7. 
