312 BRITISH SILURIAN BRACHIOPODA. 



compressa, by its convex valve being the dorsal one ; while it is the ventral one that 

 is convex in the last-named species. It differs also by several internal characters in both 

 valves. In the ventral one the muscular impressions are narrow, while they are broad 

 and saucer-shaped in St. compressa and St. expansa. Prof. M'Coy states that it is also 

 distinguished from 0. cocpansa by its much coarser striae. In some specimens the ventral 

 valve is almost flat. D'Eichwald is of opinion that the Leptcena heraldica and L. 

 exclamatoria of Kiitorga are synonyms ; but I do not know enough of those two species 

 to be able to venture an opinion. Perhaps the OrtJiis cancellata of Portlock might 

 be a variety of this shell (it is so considered at p. 545 of the 3rd edition of ' Siluria/ 

 1859) ; but here again I must confess my ignorance, not having been able to examine 

 the specimen upon which the species was founded. The shell named OrtUs grandis (Sow.), 

 by Portlock ('Rep. Geol. Londonderry,' p. 452, pi. xxxii, fig. 25, 1843) does not 

 belong to Sowerby's type, but it is referable to Orthis porcata, M'Coy. Better specimens 

 of Stroph. grandis should be sought for, so as to enable Palceontologists to complete its 

 description. 



Position and Locality. Strophomena grandis occurs chiefly in the Caradoc at 

 Horderley, Soudley, Acton Scott, and near Church Stretton ; at Dolwyddelan, Boduan, 

 Caernarvonshire; Bala, Merionethshire; and Pwll-y-wrach-uchaf and Llanfylhn, Mont- 

 gomeryshire. Mr. Salter informed me that the specimens from May Hill, labelled St. 

 grandis by M'Coy, in the Woodwardian Museum, are only fragments of St. euglypha 

 and St.filosa. 



In Ireland it occurs at Tirnasken and Badahessiagh, Pomeroy, Tyrone ; also at 

 Desertcreat, &c. 



In Scotland, near Girvan, in Ayrshire. 



M. d'Eichwald mentions it as found in Russia. 



Strophomena expansa, Soto. (sp.). PI. XLV, figs. 1 — 10. 



Orthis expansa, J. de C. Sow. Sil. Syst., pi. xx, fig. 14, 1839. 



— PECTEN, Id. (not Linue). PI. xxi, fig. 9. 



— EXPANSA, var. coNCENTEiCA, Portloclc. Rep. Geol. Londonderry, &c., p. 452, 



pi. xxxvii, fig. 1, 1843. 



— RUGIFERA — Id. p. 4.5.3, pi. xxxvii, figs. 2 a, 2 b, 1843. 

 Strophomena expansa, Phillips and Salter. Mem. Geol. Surv., vol. ii, p. 377, 1848. 

 Orthis — M'Cotj. Brit. Pal. Foss., p. 217, 1852. 



Strophomena — Salter. Siluria, 3rd ed., p. 210, fig. 2, and pi. vi, fig. 4, 



1859. 



Spec. Char. Semicircular, much depressed, rather wider than long ; hinge-line 

 nearly or quite as long as the shell, with rectangular or obtusely angular extremities ; 



