418 Systematic Paleontology 



This species is common in the Becraf t of Maryland and attains a width 

 up to 45 mm. All the specimens are single valves and the thin edges have 

 suffered abrasion before deposition, so that the species appears to be more 

 alate than in New York. None of the examples show any trace of the fold 

 or the sinus being plicated, a character of some of the New York material 

 referred by Hall to this species. Some of the smaller specimens of S. 

 concinnus are difficult to distinguish from ;S'. cyclopterus without the aid 

 of the detailed surface characters, but, as a rule, the latter have fewer and 

 more elevated plications. 



Regarding the New York material, it seems unwise to include in this 

 species the New Scotland material figured by Hall (pi. xxv, figs. 2ft-2/). 

 These specimens are unlike those of the Becraft in being more transverse 

 and larger, while the surface lamellae terminate in delicate spines, a char- 

 acter of S. cyclopterus, and not of S. concinnus. The latter has no lamellas 

 and the plications are ornamented by very delicate intermittent radial 

 lines of pustules, a character best developed among the Ostiolati spirifers, 

 to which group S. concinnus belongs. In restricting this species, as above 

 indicated. Hall's original figures and his remarks in Paleontology of New 

 York, vol. iii, have been followed, i. e., S. concinnus is here restricted to 

 the Becraft su'oquadrangular specimens in wliich the fold and sinus are 

 without plications. 



Length 2.1 cm.; width 2.4 cm. 



Occurrence. — Heldeuberg Formation, Becraft Member. Warren 

 Point, Pennsylvania; North Mountain, Maryland; Cherry Run, West 

 Virginia. 



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



SpIRIFER PROAVITUS n. sp. 



Plate LXXI, Fig. 17 



Spirifer concinmis Hall and Clarke, 1893, Nat. Hist. N. Y., Pal., vol. viii, pt. ii, 

 pi. XXX, figs. 1, 2. 



Description. — Associated with S. concinnus in New York according to 

 Hall are many specimens in which there are faint indications of a fold on 



