MARYLAND GEOLOGICAL SURVEY 205 



Genus DIPLOGRAPTUS McCoy 



DIPLOGRAPTUS VESPERTINUS (Euedemann) 



Plate LIII, Figs. 2-4 



Diplograptus pristis (parte) Hall, 1847, Pal. New York, vol. i, pi. Ixxii, 



figs. 1, la, Ib, Ik, 11. 

 Diplograptus foliaceus mut. vespertinus Ruedemann, 1908, Mem. New York 



State Mus., vol. xi, pt. 2, pp. 352-354, pi. xxv, figs. 4, 5, 18, text figs. 



296-298. 



Description. " Synrhabdosome not observed. Ehabdosomes as a rule 

 short (15 mm., greatest length observed 42 mm.), widening gradually 

 from an initial width of 1 mm. to a maximum width of 2.5 which is 

 attained in a distance of 15 mm. from the sicular extremity and then 

 maintained. Sicula not observed. Sicular extremity furnished with a 

 short blunt virgella (about .4 mm. long) and two equally short straight 

 lateral spines. Thecae numbering 11 to 13 in 10 mm. (30-32 in 1 inch), 

 inclined at an angle of 30 -40, overlapping a little more than one-third, 

 the outer margin distinctly convex, the proximal part frequently slightly 

 concave. The aperture horizontal, concave, the interthecal excavation 

 about one-fourth the width. Nemacaulus very thin and inconspicuous 

 within the rhabdosome and not seen protruding beyond the antisicular 

 end/' Ruedemann, 1908. 



The types are from the Normanskill (Chazyan) shales of New York 

 and the species has been identified also from the Trenton shales of the 

 same state. 



Occurrence. MARTINSBURG SHALE (Eden division). Jordans Knob, 

 one and one-half miles northeast of Fort Loudon, Pennsylvania, and in the 

 same horizon on the west slope of Eickard Mountain, Maryland. 



Collection. U. S. National Museum. 



