BRACHIOPODA. 83 



Genus S C H M I D T I A , Volbortii. 186!). 



1SG9. Sekmidtia, Volbortii. Ueber Schmidtiii „,id Acitis: Veiha.i.U. ,lei- Kiiss.-kiiis. Mineral. Gesell- 



.sch. zii St. Petei-sb. 2te Ser. B,i. iv, p. 213, pi. xvii, tigs. 1-6. 



Type, S. celata. Unguliten-schichten. 



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

 Hall. TlK'pedicle-valve has a broad grooved 

 area, and in the middle of the valve are 

 two rather deep depressions separated bv 

 an elevated ridge, and having abrupt '|-. i 



posterior margins, but with their anterior IV 

 edges illy defined. These features may be •; 



compared with those seen on the interior .s.hmidua ca:iui„ 



of Oboklla polita, Hall (see plate ii, fig. 38). k.o.st. in?criorTpe"dicio.vaivc. 



1„ ii „„ ;. 1 • T • 1 Fio. 3S. Interior of brachial valve, 



n tlie opposite valve is a median ridge, 



with a rather more sharply defined pair of elliptical depressions. iMr. Dall 



observes* that the name Sch.mihtia was preoccupied in 1863 for a genus of 



PoBIFEBA 



Genus MONOBOLINA, Salter. 1865. 



PLATE IV K, FIGS. 2, :l. 



1865.. Monvholina, Salter. Mem. Geol. Survey Gifat iJritain, vol. iii, p. 334, pi. xi b, fiffs. 10, 10a. 



1866. Oholellaf, Damdsok. British Silurian Bnichiopotla, p. 61, pi. iv, figi^, 20-27. 



1871. Obolusf, Davidson. British Siluri.an Brachioiioda, Appen<lix, p. 341, pi. 1, fig-s. 23, 24. 



1SS4. Oboliis, Davidson. British Silurian Bi-achiopoda. Gt^ueral Suniniai'V, p. 291. 



" Section Monobolina, muscular scars united closeh- 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. 



