230 BRITISH SILURIAN BRACHIOPODA. 
seven in width, while the width of the shell before fossilization could not have exceeded 
seven or eight. In other cases the shell was similarly elongated or twisted to one or 
other side in the most irregular manner. JI am not acquainted with any other localities 
than those above recorded. 
Ortuis Hicxsn, Salter, MS. Pl. XXXIIIL, figs. 13—16. 
Ortuis Hicks, Dav. Geol. Mag., vol. v, p. 314, pl. xvi, fig. 17—19, July, 1868. 
Spec. Char. Shell small, transversely oval; hinge-line shorter than the greatest 
breadth of the shell; cardinal angles rounded. Dorsal valve semicircular, moderately 
convex, slightly longitudinally depressed along the middle. Ventral valve convex, deeper 
than the opposite one. Area triangular, moderately wide; surface of valves ornamented 
by about ten principal, narrow, radiating ribs, with wide interspaces between each pair, in 
the middle of which is situated a shorter rib. 
Length about 4, width 5 lines. 
Obs. Orthis Hicksii is a scarce fossil, and very rarely found even in a passably com- 
plete condition. It was discovered by Mr. Hicks in the middle (sandstone) beds of the 
Menevian group at Ninewells and Porth-y-rhaw, near St. David’s, and is the oldest 
species of the genus on record. It has not been hitherto found in North Wales, nor, to 
my knowledge, in any other locality. 
Oxrais LENTICULARIS, Wahlenberg (sp.)? Pl. XXXIII, figs. 22—28. 
? ANOMITES LENTICULARIS, Wahlenberg. Nova Acta Upsal., vol. viii, p. 66, 1821. 
? ATRYPA — Dalman. Kongl. Vetenskaps Acad. Hand., p. 132, 1827. 
? SprRIFER — Von Buch. Berl. Akad., 1834, p. 48, pl. i, figs. 13, 14. 
OrrHis — Salter. Mem. of the Geol. Survey, vol. iii, p. 339, pl. iv, 
figs. 8—10, 1866. 
— — Dav. Geol. Mag,, vol. v, pl. xvi, figs. 20—22, July, 1868. 
Spec. Char. Shell small, transversely oval, nearly straight or slightly indented in 
front, wider than long ; hinge-line nearly as long as the breadth of the shell. Dorsal 
valve moderately convex, with a broad longitudinal depression, commencing at the umbone, 
and, gradually widening as it nears the front, is bounded by two rather prominent ribs, 
the sinus being occupied by two or three smaller ones. On each of the lateral portions 
are three or four principal ribs, with a shorter one occupying the centre of the wide 
interspace left between each of the larger ribs. Ventral valve convex, deeper than the. 
