BRACHIOPODA. 83 



Genus SCHMIDTIA, Volborth. 1869. 



1S(J9. Schmidtia, Volboetii. Ueber Schmidtia und Acritis : Verhandl. der Russ.-kais. Mineral. Gesell- 



sch. zu St. Petei'sb. 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 Leotobolus, 

 Hall. The pedicle-valve has a broad grooved ' ^\ 

 area, and in the middle of the valve are _ -""^^ <^?S^" 



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 schmidtia caiata. 



of Obolella polita, Hall (see plate ii, fig. 38). . fig. 37. interior of pedlcle-valve 



. , . . , Fig. 38. Interior of brachial valve. 



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 1(S63 for a genus of 



PoRIFEMA. 



Genus MONOBOLINA, Salter. 1865. 



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



1865. Monobolina,S ALTER. Mem. Geol. Survey Great Bi-itain, vol. iii, p. 334, pi. xi b, figs. 10, 10a. 



1866. OboUUa?, Davidson. British Silurian Brachiopoda, p. 61, pi. iv, figs. 20-27. 



1871. ObohiS?, DAViDSoif. British Silurian Brachiopoda, Appendix, p. 341, pi. 1, figs. 23, 24. 

 1884. Obolm, Davidson. British Silurian Brachiopoda, General Summaiy, 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. 



