38 BRITISH DEVONIAN BRACHIOPODA. 



not a character or feature of Roemer's type. I have been led to this impression from the 

 study of fig. 9, g and //, of Schnur's Sp. undifera ; and it appears to me that Dr. Sandberger 

 is, perhaps, mistaken while excluding this modification from the varieties of the last-named 

 species. I possess, likewise, a similar specimen from the Eifel, sent me some years ago by 

 Herr F. Roemer, and labelled Sp. curvatus, Schl., var. undulatus, F. Roemer, and this, 

 although quite distinct from Schlotheim's figures of Sp. curvatus, which represents a 

 smooth shell without lateral ribs, does closely resemble some varieties of the shell we are 

 at present describing. I may, however, be mistaken in my appreciation of this matter, but 

 have been unable to identify the shell with any other known Devonian species, and could 

 hardly venture to apply to it a new specific denomination. When we examine a large number 

 of specimens of Sp. undifera and of the variety (?) undulata, we can perceive a far greater 

 connection between the two than the necessarily limited selection of illustrations will here 

 convey, and this leads me to believe that the whole series of specimens figured in PI. VII. 

 do probably belong to a single but variable species. We find similar modifications to 

 occur with the Carboniferous Sp. ovalis, Sp. pinguis, and its variety Sp. rofundata. 

 Indeed, the resemblance between these Devonian shells and those last named are often 

 so very striking as to almost lead one to believe that they are all mere modifications in 

 shape of a single species. 



Sp. undifera, var. undulata, occurs plentifully in company with Sp. undifera in the 

 Middle Devonian limestone of Woolborough Quarry, near Newton Abbot. 



Spirifera nuda, Sow. PL IV, figs. 17 — 24. 



Spirifera nuda, Sow. Trans. Geol. Soc, 2nd series, vol. v, pi. lvii, fig. 8. 



— pulchklla, Soto. Ibid., fig. 9. 



— nuda, Phillips. Pal. Foss., p. 78, pi. xxxi, fig. 138, 1841. 



Spirifer nudus, F. Roemer, in Dunker's Palaeontographica, vol. v, pi. iv, fig, 20, 1855. 



Spec. Char. Shell transversely semicircular, wider than long ; dorsal valve moderately 

 convex ; mesial fold smooth, sharply defined, but of small elevation, one or two rounded 

 ribs existing on either of the lateral portions of the valve close to the mesial fold, the 

 remaining unoccupied lateral space being smooth ; hinge-line shorter than the width of 

 the shell ; cardinal angles rounded. Ventral valve deeper than the opposite one, with a 

 shallow sinus, and one or two ribs on either side ; beak prominent, angular, more or less 

 bent backwards, with its extremity incurved ; fissure partly closed by a pseudo-deltidium. 



Length 11, width 13 lines; but the shell is usually smaller. 



Obs. This interesting species varies to some extent, on account of the greater or 

 smaller proportions of its area and number of ribs. In some specimens the mesial fold 

 and sinus are alone observable, all the remaining portion of the valves being smooth (fig. 

 17). In other examples (figs. 19 — 21) there exists one rounded rib on either side of the 



