DISCINID &. 75 
P OrBicuLo1DEA Becxerriana, Dav. Pl. VII, fig. 19. 
Spec. Char. Longitudinally oval; upper or free valve conoidal or limpet-hke, and 
moderately elevated, the vertex being situated at about one third of the length of the 
valve from the posterior margin. External surface covered with numerous concentric, 
rounded ridges ; these ridges becoming wider as they approach the middle, and again 
gradually smaller as they get nearer to the margin; one specimen, showing as many as 
fifty of these rounded ridges, measured— 
Length 5 inches 5 lines, width 4 inches 8 lines. Attached valve unknown. 
Ods. It is with considerable uncertainty that I refer this fragment to the Brachio- 
poda at all; and Mr. Salter, who has arranged it for many years as possibly a Descina, 
in the Museum of Practical Geology, shares my doubts. It appears, however, to both of 
us, to be unlike anything else ; and, as two incomplete specimens only, in the condition 
of casts, were found by Mr. H. Beckett m the Wenlock limestone of the Wren’s Nest, 
Dudley, we must wait for further information. If the discovery of more complete 
examples should confirm our present supposition, this is by far the largest species of 
the genus, and, indeed, almost the largest Brachiopod, hitherto discovered. 
Genus—SivHonotreta, De Verneuil, 1845. 
Ref. De Verneuil, ‘Russia and Ural Mountains,’ vol. ii, 1845. See also Kutorga, 
‘Ueber die Siphonotretez, Verhandlungen der Kaiserlichen Mineralogischen Gesellschaft’ 
fir das Jahr, 1847. Davidson, ‘ British Fossil Brachiopoda,’ vol. i, Introduction, p. 131. 
In the Silurian rocks of Great Britain two species have been discovered, namely, 
Stphonotreta Anglica and S. micula. 
Srpponorreta Anexica, Morris, 1849. Pl. VIII, fig. 1. 
SrpHonotreta Anaeutca, Morris. Annals of Nat. Hist., 2nd ser., vol. iv, p. 320, pl. vii, 
fig. 1,a—e, 1849. 
— M‘Coy. British Pal. Foss., p. 188, 1852. 
— — Salter. Siluria, 2nd edit., p. 212, fig. 3, 1859. 
Spec. Char. Shell ovate longitudinally; dorsal valve very slightly convex or 
depressed, ventral valve most convex and deepest about the middle ; beak produced, with a 
small oval perforation or foramen at its extremity. The surface of each valve is marked 
