596 Systematic Paleontology — Upper Devoxian 



4596, 4631, 4716 abnudant, 4769 abundant; 2 miles west of Pawpaw, 

 West Virginia, 2124 abundant, 2190, 4564 abundant, 4694; Fifteemnile 

 Creek, 1 mile above Little Orleans, 2216, 2286; National Eoad, on Green 

 Ridge, 1850; Woodmont, 1667; Hancock, 2275; Millstone 2390 abundant, 

 2440, 2919; National Eoad, 5-7 miles west of Frostburg; Oakland- 

 Altamont Road; Green Glade Run; various places near Oakland and 

 Deer Park ; vicinity of Trout Run ; near top of Chemung east of Barrel- 

 ville; Wills Creek Station, Pennsylvania. 

 Collection. — Maryland Geological Survey. 



Spirifee mesastrialis Hall 

 Plate LVII, Figs. 2-5 



Spirifer mesastrialis Hall, 1867, Pal. of N. Y., vol. iv, p. 242, pi. xl. 



Spirifer viesastrialis Hall and Clarke, 1894, Ibid., vol. viii, pt. ii, pi. xxxvii, 



figs. 4, 5. 

 Spirifer mesastrialis Grabau and Sliimer, 1909, N. Amer. Index Foss., vol. i, 



p. 332, fig. 423. 



Description. — -This Spirifer is characterized by the fine radial lines 

 Avhich cover fold and sinus and also traverse the numerous flattened 

 lateral plications and furrows of the valves. At times these lineations 

 become interrupted, specially near the margins of the median part of the 

 shell and appear as radial series of elongate pustules. The form of the 

 valves is quite variable, sometimes short on the hinge, plump and round, 

 again with elongated cardinal extremities ; the size of the shell prevailing 

 at a given locality may be large, medium or small, but for all these varia- 

 tions the laws governing their manifestations have not yet been as- 

 certained. Aniong them all it is usual to find the plications, 10 to 15 

 in number, moderately broad and flattened, with narrow furrows and fold 

 and sinus low and near the anterior margin very broad. Concentric 

 markings or growth lines are usually absent. 



Length 25 mm.; width 45 mm. 



The figures we have given show the characteristic expression of this 

 shell in Maryland. In New York the species is a survivor from the fauna 

 of the Itliaca where it is introduced into that favma soon after its return 

 to the field it lield. before the close of Hamilton time. In the middle 



