688 SYSTEMATIC Paleoxtology — Upper Devonian 



Description. — " Shell an extremely elongate, gradually and regularly 

 tapering cone, having in the largest individuals a diameter of six mili- 

 meters at the larger extremity, \Yith a length of seventy-five millimeters. 



Surface marked by fine closely arranged stria\. or frequently with more 

 distant oblique annulations, receding from the aperture, or sinuate on the 

 ventral side — the degree of obliquity depending upon the position of the 

 fossil, or the relation of the parts exposed to view. Interrupted longi- 

 tudinal stri^ are visible in well-preserved specimens." Hall, ISTD. 



This is an abundant and characteristic species of the Parkhead fauna. 

 The specimens observed agree well with those figured by Hall from the 

 Hamilton of New York. Some shells attain a somewhat greater size than 

 those described by him. 



Occurrence. — Jennings Formation, Chemung Member. Two miles 

 north of mouth of Town Creek, 1949; Town Creek, 2G91; upper Tropi- 

 doleptus zone ? northeast of Pratt near Pennsylvania-Maryland state 

 line. Parkhead Member. Williams Eoad, on Polish Mountain, 1660 

 abundant; 2 miles north of mouth of Town Creek, 1842; 4 miles southeast 

 of Pratt abundant; Town Creek, 1679; 2 miles west of Pawpaw, 1493, 

 1799; Little Orleans abundant; Fifteenmile Creek, 1 mile above Little 

 Orleans, 1746. 



Collection. — Maryland Geological Survey. 



Family HYOLITHIDAE 



Genus HYOLITHES Eichwald 

 Hyolithes aclis Hall 

 Plate LXXI, Figs. 7-9 



Hyolithes aclis Hall, 1876, Illustrations Devonian Foss., Pteropoda, pi. 



xxvii, flgs. 5-7, 10, 11. 

 Hyolithes aclis Hall, 1879, Pal. of N. Y., vol. v, pt. ii, p. 197, pi. xxxii, figs. 



22-30; pi. xxxiia, figs. 23-25. 

 Hyolithes aclis Cleland, 1911, Bull, xxi, Geol. Surv. Wis., p. 132, pi. xxvi, 



fig. 8. 



Description. — " Form an elongate triangular pyramid, gradually and 

 regularly tapering to an acute extremity. Transverse section somewhat 



