166 



BRITISH SILURIAN BRACHIOPODA. 



Smotrytscli, near the village of Laskovsky, in Podolia ; also from the Island of Oesel. 

 In America it is stated by J, Hall to occur in the shale at Lockport in the Niagara 

 Group, also on the Niagara River above Lewiston. 



Rhynchonella Stricklandii, /. de C. Soio. (sp.). PI. XXI, figs. 1 — 6, and 28. 



Tekebratula Stricklandii, J. de C. Sow. Sil. Sjst., pi. xiii, fig. 19, 1839. 



— CRisrATA, Id. lb., pi. xii, fig. 1 1, 1839. 



— Stricklandii, Dav. Bull. Soc. Geol. France, 2nd ser., vol. v, p. 329, 1848. 

 Hypothyeis — Phillips and Salter. Mem. Geol. Survey, vol. ii, part 1, 



p. 282, 1848. 



Hemithyris — B'Orhigny. Prodrome, vol. i, p. 37, 1849. 



— — M'Coy. Brit. Pal. Foss., p. 206, 1852. 

 Rhynchonella — Morris. Catalogue of British Fossils, p. 146, 1854. 



— — Salter. Siluria, 2ud ed., pp. 250 and 544, pi. xxii, 



fig. 11, 1859. 



— — Lindstrom. Ofv. K. Vet. Akad. Forhandl, p. 366, 1860. 



Spec. Char. Transversely ovato-subtrigonal, very convex, somewhat wider than long, 

 sides and front rounded. Dorsal valve gibbous or ventricose, slightly flattened at the 

 umbone, pinched in or concave laterally ; mesial fold wide, not commencing until at 

 some distance from the umbone, and becoming more prominent as it approaches the 

 front. Ventral valve not quite as deep or convex as the dorsal ; sinus wide and rather 

 deep ; beak very small, depressed, and incurved over, and appressed to the umbone of 

 the dorsal valve; lateral spaces wide, concave, and indenting by a convex curve the 

 corresponding margin of the opposite valve. Surface of each valve ornamented with from 

 twenty-eight to thirty-four narrow, simple, angular ribs, which radiate from the beaks to 

 the margins, and of which six or eight occupy the fold and sinus. Two specimens 

 measured — 



Length 15, width 16, depth 13 hues. 

 » 12 „ 131 „ 8 „ 



Obs. This well-marked species varies a good deal according to age and circumstances. 

 When quite young it is much depressed, the fold and sinus being hardly apparent, but 

 with age the shell becomes globose, the ventral valve often ventricose, especially posteriorly, 

 while the fold acquires its greatest elevation near the front. The smallness of the 

 flattened appressed beak, and the concave or pinched-in lateral portions of the beak and 

 umbone, give to this species a well-marked and easily recognizable character. Some 

 internal casts show beautifully the muscular and vascular impressions (fig. 6). At 

 p. 1231 of his 'Index Palacontologicus,' Bronn places Rh. Stricklandii among the 

 synonyms of Rh. horealis ; but this is quite a mistake, as a glance at their respective 

 figures will at once show ; and it is probable that the distinguished German palaeonto- 



