Maryland Geological Survey 309 



viduals never reaching a large size, nearly entire examples have a length 

 of from 85 to 130 mm. 



The Maryland specimens are fragmentary and very imperfectly pre- 

 served ; but smooth internal molds and fragments of external impressions 

 with the outline and markings of this species have been referred to it. 

 On comparison they were found to agree fairly well with specimens 

 labeled as this species which are in the office of the State Paleontologist of 

 New York; while the smooth, internal impression of a living chamber 

 which is figured was submitted to Dr. J. M. Clarke, who reports that it 

 is probably safe to refer it to 0. suhulatum Hall rather than 0. constric- 

 tum Van., since the constriction is Avanting which is the most important 

 difference between the two species. 



The longest fragment in the collection has a length of 60 mm. 



Occurrence. — Eomney roRMATiON, Onondaga Member. Williams 

 Eoad, 31/2 miles southeast of Cumberland. Hamilton Member. On W. 

 Va. side Potomac Eiver 3 miles south of Cumberland ; on road about half 

 way between Eomney and Hanging Eock, W. Va. ( ?) . 



Collection. — -Maryland Geological Survey. 



Orthoceras constrictum Vanuxem 

 Plate XXXIX, Figs. 5-8 



Orthoceras constrictum Vanuxem, 1842, Geol. N. Y., pt. iii, p. 152, fig. 1. 

 Orthoceras constrictum Hall, 1862, Fifteenth Rep. State Cab. Nat. Hist., p. 77. 

 Orthoceras constrictum Hall, 1879, Pal. N. Y., vol. v, pt. ii, p. 288, pi. Ixxxiv, 



figs. 13, 14, 16; pi. Ixxxv, figs. 5, 10, 11, 13. 

 Orthoceras constrictum Keyes, 1891, Johns Hopkins Univ. Circ, vol. xi, p. 29. 

 Orthoceras constrictum Clarke, 1903, N. Y. State Mus., Bull. 65, p. 621. 

 Orthoceras constrictum Clark and Mathews, 1906, Md. Geol. Surv., vol. vi, 



pi. xvii, fig. 14. 

 Orthoceras constrictum Grabaii and Shimer, 1910, N. Am. Index Fossils, vol. 



ii, p. 51, fig. 1251. 



Description. — Shell straight, regularly enlarging from the apex to the 

 chamber of habitation; transverse section circular. Living chamber cylin- 

 drical, well developed, having a length equal to four times the diameter at 

 the last septum ; anterior to the middle there is a very broad, gentle con- 

 striction, which, in its position and strength, varies considerably, some- 



