BRACHIOPODA. 
83 
Genus SCHMIDTIA, Volborth. 1869. 
1869. Schmidtia, Volborth. Ueber Schmidtia und Acritis: Yerhandl. der Russ.-kais. Mineral. Gesell- 
sch. zu St. Petersb. 2te Ser. Bd. iv, p. 213, pi. xvii, figs. 1-6. 
Type, S. celata. Unguliten-schichten. 
The shells of this genus have the form and external characters of Le|)tobolus, 
Hall.. The pedicle-valve has a broad grooved 
area, and in the middle of the valve are 
two rather deep depressions separated by 
an elevated ridge, and having abrupt 
posterior margins, but with their anterior 
edges illy defined. These features may be 
compared with those seen on the interior 
of Obolella polita, Hall (see plate ii, fig. 38). 
In the opposite valve is a median ridge, 
with a rather more sharply defined pair of elliptical depressions. Mr. Dall 
observes* that the name Schmidtia was preoccupied in 1863 for a genus of 
P ORIFEBA. 
Genus MONOBOLINA, Salter. 1865. 
PLATE IV K, FIGS. 2, 3. ’ 
1865. Monobolina, Salter. Mem. Geol. Survey Great Britain, vol. iii, p. 334, pi. xib, figs. 10, 10 a. 
1866. Obolella ?, Davidson. British Silurian Brachiopoda, p. 61, pi. iv, figs. 20-27. 
1871. Obolus?, Davidson. British Silurian Brachiopoda, Appendix, p. 341, pi. 1, figs. 23, 24. 
1884. Obolus, Davidson. British Silurian Brachiopoda, General Summary, p. 291. 
“ Section Monobolina, muscular scars united closely along the central line.” 
Salter ( loc . cit.). 
Type, Lingula plumbea, Salter. 1859. Lower Llandeilo. 
The later figures given by Mr. Davidson of the interior of the type-species 
show that the peculiar concentration of the muscular impressions as indicated 
by Mr. Salter, is strikingly different from anything seen in Obolus, Obolella, 
* Bull. U. S. Nat. Mus., No. 8, p. 62. 
