MARYLAND GEOLOGICAL SURVEY 337 



gently convex, and the margin abruptly bent down or bevelled nearly 

 vertically, the upper edge of the bevel angular and with indications of a 

 slightly elevated linear rim; axis very depressed convex or nearly flat, 

 its width at the anterior margin about one-fourth of the whole width, 

 extending the whole length or nearly so, crossed by obscure undulating 

 furrows. Side lobes gently convex. 



u Length of the head without the rostrum, 5 or 6 lines ; length of the 

 pygidium about 4 lines." Billings, 1865. 



Fragmentary specimens of an Ampyx from the Echinospherites bed of 

 Maryland and Pennsylvania agree so closely with Billings' figures and 

 description that they are believed to represent the same species in spite 

 of the differences in horizons. 



Occurrence. CHAMBERSBURG LIMESTONE (Echinospherites bed). 

 Southern Pennsylvania and at Pinesburg Station, Maryland. 



Collection. U. S. National Museum. 



AMPYX (LoNCHODOMAs) HALLI Billings 

 Plate XXXIX, Figs. 9-11 



Ampyx halli Billings, 1862, Kept. Econ. Geol. Vermont, p. 231, text fig. 365. 

 Ampyx halli Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 24, text 



figs. 25a-c. 

 Lonchodomas halli Raymond, 1905, Ann. Carnegie Mus., vol. iii, No. 2, 



p. 332, pi. x, figs. 3-7. 



Description. " Cephalon. Cranidium triangular, the greatest width 

 at the neck segment. The glabella extends about half its own length 

 beyond the anterior angles of the fixed cheeks, and is then prolonged into 

 ci long, fluted spine, which curves gently upward. This spine is pris- 

 matic, with a deep furrow on each of its four sides. The furrow on the 

 upper side extends back to about the region of the fixed cheeks. Glabella 

 widest at the anterior angles of the fixed cheeks, and contracting pos- 

 teriorly, so that it forms about one-fifth of the whole width at the neck 

 segment. On the cast there are two small nodes on each side of the 

 glabella near its posterior end, one pair a little in front of the other. A 

 distinct carina extends along the top of the glabella to the posterior end 

 of the dorsal furrow on the rostrum. 



