Mauylaxd CJeological Survey 407 



vortical stria} or crenulations [these are tubular spines] which project in 

 fimbria? on the edge of the lamellpe." Hall, 1857. 



This well-known New York species occurs abundantly in Maryland, but 

 is rarely well preserved. In the southern material the fimbriate lamella? 

 are less crowded than in the New York individuals, and in this they ap- 

 proach more nearly to S. tribulis of the Lower Oriskany. In the Cumber- 

 land region there need be no difficulty in distinguishing 8. cyclopterus 

 from the associated Spirifers, but in Washington County, where the Be- 

 craft member is present, it may be confounded with small specimens of 

 8. concinnics. However, the latter generally attains a larger growth, has 

 more numerous and depressed plications, and when the fine surface detail 

 — a rare feature — is preserved, it will be seen to be devoid of the fimbriate 

 lamellae. 



Length 1.7 cm.; width 2.6 cm. 



It is probable that the pauciplicate form of 8. cijdopterus gives rise to 

 8. tribulis, while the more abundantly plicate specimens develop into 8. 

 intermedins. However, it may be that the latter arises directly from 

 8. tribulis. 



Occurrence. — Heldekberg Formation, Coeymans and New Scot- 

 land Members. This species is abundant in Allegany and Washington 

 counties. Becraft Member. Washington County. 



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



Spirifer tribulis Hall 

 Plate LXIX, Figs. 11-14 



Spirifer tribulis Hall, 1859, Nat. Hist. N. Y., Pal., vol. Hi, p. 420, pi. xcvi, flgs 



Sa-Se, 1861. 

 Spirifer tribulis Hall, 1883, Second Ann. Rept. N. Y. State Geol., pi. Iviii, figs, 



1-4. 

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



pp. 19, 37, pi. xxxiii, flgs. 1-4. 



Description. — " Shell transverse, varying from semicircular to sen ' 

 elliptical; cardinal extremities more or less rounded, gibbous in the 

 middle. Ventral valve more convex than the dorsal: beak elevated and 

 incurved; sinus narrow and shali(>\v above, becoming deeper and sub- 



