Maryland Geological Survey 409 



Spirifer angularis n. sp. 

 Plate LXIX, Figs. 15, 16 



Description. — This species is related to S. irihulis, S. intermedius, but 

 more particularly to S. murchisoni. However, it cannot be referred to any 

 one of these fonns. With S. trihulis it will not be confounded because the 

 two are not found associated and S. angularis attains a larger size with a 

 greater number of plications. Of the latter there are from seven to nine 

 on each side of the median fold in S. angularis. From S. intermedius it is 

 distinguishable by its smaller size and fewer and more angular plications ; 

 from S. murchisoni, by its smaller size, narrower fold and sinus, and 

 greater alation. 



Length 3 cm. ; width 3.3 cm. 



The specimen figured has the sinus and fold sharply angulated, which 

 is the case in about one-half the individuals, while the remainder have 

 those parts more rounded. In some respects S. angularis may be regarded 

 as immature 8. murchisoni var. marylandicus, but the uniformly smaller 

 size and the comparatively greater alation prevent such a reference. 



S. angularis is also related to the common Lower Devonian 8. hystericus 

 Schlotheim of the German Siegen.^ The American form is distinguished 

 by being less alate, having a higher ventral cardinal area, and especially 

 by the fact that the German species never has the deeply excavate muscular 

 area so characteristic of this species and 8. murchisoni. 



Occurrence. — Oriskany Formation, Eidgely Member. Eidgely; 

 Miller's Springs, West Virginia. 



Collections. — Maryland Geological Survey, U. S. National Museum. 



Spikieer intermedius Hall 

 Plate LXIX, Figs. 17-31 



Spirifer intermedius Hall, 1859, Nat. Hist. N. Y., Pal., vol. ill, pp. 424, 430 

 (not S. intermedius (Schlotheim), 1813). 



Description. — " Shell transverse, semielliptical ; the ventral valve mod- 

 erately and regularly convex, area of medium height, foramen large; 



' See Dreverman, 1904, Palaeontographica, vol. 1, p. 253, pi. xxx, flgs. 17. 



