BRACHIOPODA. 



83 



Genus SCHMIDTIA, Volborth. 1869. 



1S09. Schmidtia, Volborth. Ueber Schmidtia und Aoritis : Verhandl. der Russ.-kai.<5. Mineral. Gesell- 



sch. zu St. Petei'sb. 2te Ser. Bd. iv, ji. ai.S, pi. xvii, fig-s. 1-6. 



Type, S. celata. Unguliten-schichten. 



The shells of this genus have the form and external characters of Leotobolus, 

 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 



PolilFERA 



Schmidtia ccelata. 



After Volborth. 

 Fig. 37. Interior of pedicle-valve 

 Fig. 38. Interior of brachial valve 



Genus MONOBOLINA, Salter. 1865. 



PI.ATE IV K, FIGS. 2, 3. 



1865.. Monoholina, Salter. Mem. Geol. Survey Great Britain, vol. iii, p. 334, pi. xi b, tig'.". 10, 10a. 



1866. Obolella?, Davidson. British Silurian Bracliiopoda, p. 61, pi. iv, figs. 20-2J. 



1871. Obnltis?, Davidson. British Silurian Brachiopoda, Appendix, p. 341, pi. 1, tigs. 23, 24. 



1884. Oboliis, 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. 



