344 BRITISH SILURIAN BRACHIOPODA. 



believes lie has found it, or another (undeterminable) allied form, in the upper portion of 

 the " Arenig Group" at Whitesand Bay, St. David's, South Wales. 



Genus — Discina, Lamark, 1819. 

 (See 'General Introduction,' p. 126 ; and supra, p. 63.) 



Discina (Trematis) corona, Salter, MS. PI. XLIX, figs. 43, 44. 



Of this species there are two incomplete examples in the Cambridge Woodwardian 

 Museum. The shell is not, however, sufficiently perfect to be described satisfactorily. It 

 is nearly circular in outline. The upper or free valve is moderately convex or conical, 

 with the apex at about one third the length of the shell from the margin. The outer 

 surface is covered with close-set rows of small cells or sunken dots, about twelve rows 

 near the margin occupying a breadth of two lines. The rows of dots radiate from the 

 apex. 



Length about 20 lines, by rather less in breadth. 



Position and Locality. This shell occurs in Bala Shales at Dufton Pusgill, in West- 

 moreland. A search for better examples of this interesting species should be made. 



Discina pileolus, Hicks. PI. XLIX, figs. 41, 42. 



Discina pileolus, Sicks, MS. Report Brit. Assoc, for 1865, p. 285, 1866. 

 — — Bav. Geol. Mag., vol. v, p. 312, pi. xvi, figs. 11—12, 1868. 



Sjjec. Char. Shell very small, circular or slightly longitudinal oval, rather broader 

 anteriorly ; about two and a half lines in length and a little less in breadth. Dorsal valve 

 conical ; ventral valve slightly convex, depressed near the margin ; vertex in both valves 

 at a short distance from the centre, as also the foramen (?) in the ventral valve. Surface 

 marked with concentric lines, which are more strongly marked in the ventral valve. In- 

 terior not known. 



Obs. Mr. Salter was the first to detect the presence of this genus in the '' Maenevian 

 Group," and the species under notice subsequently received the designation of '■' pileolus y 

 from Mr. Hicks. We have already stated that the so-termed Discina lahiosa (Salter) was 

 founded on the internal cast of the ventral valve of Oholella sagittalis. 



Position and Locality. Discina pileolus was found by Mr. Hicks in the Middle beds 

 (Sandstone) of the " Maenevian Group" at Porth-y-rhaw, Ninewells, and Solva Llarbour, 

 St. David's, where it is scarce and usually very imperfectly preserved. A minute Discina 

 ■was found by Mr. Hicks in one of the yellowish-grey beds of the " Harlech Group/' on 



