34 BRITISH DEVONIAN RRACHIOPODA. 



extremities; valves convex, with a smooth fold in the ventral valve. From twenty to 

 twenty-four angular ribs ornament the surface of each valve, the whole being traversed by 

 numerous concentric lines or slightly prominent laminge. Beak almost straight; area flat, 

 triangular, comparatively large ; fissure partly arched over by a pseudo-deltidium. Two 

 specimens have measured — 



Length 10, width 14^, depth 6 lines. 

 7 17 7 



Obs. Professor De Koninck and M. Bouchard are of opinion that the shell above 

 described should be referred to Sp. sub-cuspidatus, Schnur, and that it is specifically 

 distinct from the Hysteriolites hystericus of Schlotheim (?). Professor Schnur, however, 

 mentions as synonyms of his species Delthyris microptera, Goldfuss, and Hysterolites 

 hystericus of Schlotheim ; but, if this was his opinion, I cannot understand why he did not 

 adopt one of the two designations, instead of proposing a new name for the shell under 

 description. 



Sp. sub-cuspidata occurs in the Middle Devonian limestone of Woolborough, near 

 Newton Abbot, and at Hope's Nose, near Torquay. On the Continent it is a common 

 fossil in the Eifel. 



Spirifera hysterica, Schlotheim (?). (sp.) PI. VIII, figs. 16, 17. 



Hystehtolites hystericus, Schlotheim. Erklarung der AbbilJuugen der zu diesem Werke 



gehorigen Kupfertafeln, Petrefactenkunde, pi. xxix., fig. 1 "• h , 

 1822. 

 Spikifeu micropterus, D'Jrchiuc, De Verneuil, and J. De C. Sow. Descript. of the 



Fossils of the Older Rhenish Provinces, Trans, of the Geol. 

 Soc, 2nd series, vol. vi, pp. 394 and 408, pi. xxxviii, fig. 6: 

 (not of Goldfuss?). 



Spec. Char. Shell transversely semicircular or sub-pentagonal ; hinge-line almost as 

 long as the width of the shell ; dorsal valve moderately convex ; fold simple, sharply defined, 

 rounded ; ventral valve deeper than the opposite one, with a shallow sinus. Surface of 

 each valve ornamented by from twenty-six to thirty simple ribs ; beak slightly incurved ; 

 area triangular, of moderate width ; fissure partly covered over by a pseudo-deltidium. 



Length 1 2, width 1 7 lines. 



Obs. Impressions and internal casts of the shell under description do not appear 

 rare in the Middle Devonian (?) yellowish grits of Linton, in North Devon ; but the 

 absence of the shell itself precludes the possibility of our arriving at a positive conclusion 

 as to its specific identification. 



In external shape, character of fold, and number of ribs, it so nearly approaches 

 Schlotheim's figures of //. hystericus that I have ventured to provisionally leave it under 

 that designation. It also closely resembles the figures given by J. De C. Sowerby in 



