336 SYSTEMATIC PALEONTOLOGY 



Several distinct species are doubtless included in the many descriptions 

 that have been published under the name of Cryptolithus tesselatus and 

 more particularly Trinucleus concentricus. The specimens from the base 

 of the Martinsburg shale, however, are undoubtedly the same specifically 

 as the Trenton forms upon which Green and Hall based their figures and 

 descriptions. The New Jersey Trenton specimens described as above 

 by Weller likewise belong to the same species. 



This species is generally quoted as ranging from the base of the 

 Trenton to the middle part of the Maysville group, but the species when 

 restricted will probably be found to be limited to the Trenton rocks. In 

 Pennsylvania and southward it occurs in the Sinuites zone of the Trenton 

 at the base of the Martinsburg shale. 



Occurrence. MARTINSBURG SHALE (Sinuites and Corynoides beds). 

 Williamsport, Maryland, and Chambersburg, Pennsylvania. 



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



Family RAPHIOPHORIDAE 



Genus AMPYX Dalman 



AMPYX (LoNCHODOMAs) NORMALIS (Billings) 

 Plate XLV, Figs. 13, 14 



Ampyx normalis Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 295, 



text fig. 286. 

 Ampyx (Lonchodomas) normalis Grabau and Shimer, 1910, N. A. Index 



Fossils, vol. ii, p. 259. 



Description. " Head, without the movable cheek, triangular, the width 

 about one-third greater than the length; fixed cheeks, gently convex, 

 smooth; neck segment consisting of a flat plate, inclining backwards. 

 The glabella elongate-ovate, greatest width about the mid-length, one- 

 fourth narrower at the neck segment, the apex extending a little over the 

 front margin of the head; the rostrum, apparently, when perfect, equal 

 to the whole length of the head, not round but fluted ; two or three ovate 

 or nearly circular scars, one each side of the glabella in the posterior half. 



" Pygidium triangular, width twice the length, the two posterior sides 



