434 Systematic Paleontoj.ogy 



narrow, extending to the apex of the beak of the ventral valve, partly 

 closed above by a central plate. Surface marked by nine to eleven ele- 

 vated angular costse on each side of the middle, crossed by strong im- 

 bricating concentric lamellse." Hall, 1857, 



This well-known species of Cyrtina is not rare, and occasionally a speci- 

 men of Spirifer intermedius is found with young examples still attached. 

 Mr. Hartley has such a specimen with thirteen young of various ages all 

 lying on their flat ventral cardinal areas, and this undoubtedly is their 

 position in life. In the youngest stages this species is greatly alate, but 

 toward maturity growth becomes strongest anteriorly, when the shells 

 are comparatively less drawn out on the hinge-line. 



To C. rostrata are also referred two examples from the Becraft. One, 

 a dorsal valve, cannot be distinguished from typical specimens from the 

 Upper Oriskany. The other is an entire individual, is decidedly alate, has 

 nine plications on each side of the fold or sinus, and the dorsal valve is 

 nearly flat. The same variation also occurs, but rarely, among the typical 

 specimens of C. rostrata. 



Length 10 mm. ; width 21 mm. 



Occurrence. — Helderberg Formation, Beci^vft Member. Cherry 

 Run, West Virginia. Oriskany Formation, Ridgely Member. Knobly 

 Mountain near Cumberland, common. 



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

 American Museum of Natural History. 



Family RHYNCHOSPIRID/E 



Genus RHYNCHOSPIRA Hall ' 



Rhynchospira rectirostra (Hall) 

 Plate LXXII, Figs. 13-15 



Waldheimia rectirostra Hall, 1857, Tenth Ann. Rept. N. Y. State Cab. Nat. 



Hist., p. 89. 

 Trematospira (Rhynchospira) rectirostra Hall, 1859, Nat. Hist. N. Y., Pal., 



vol. iii, p. 217, pi. xcva, fig. 1, 1861. 



Description. — " Shell longitudinally ovate, tapering towards the beak 

 at an angle of about 45°, slopes on each side of the beaks, flattened and not 



• See Hall and Clarke, 1893, Nat. Hist. N. Y., Pal., vol. viii, pt. ii, p. 108. 



