MARYLAND GEOLOGICAL SURVEY 327 



and apparently rather deeply concave. Siphon near the inner margin 

 of the tube and comparatively large. 



The few examples of this fine cephalopod discovered in Maryland do 

 not preserve all the surface features mentioned above, but they agree in 

 size and general outline. 



Occurrence. BEEKMANTOWN LIMESTONE (Turritoma zone). Stouf- 

 ferstown, Pennsylvania, and east of Huyett, Maryland. Fort Cassin, 

 Vermont. 



Collection. U. S. National Museum. 



TROCHOHTES AMMONIUS Conrad 



Plate L, Fig. 43 



Trocholites ammonius Conrad, 1838, 2d Ann. Kept. New York Geol. Surv., 



p. 119. 

 Trocholites ammonius Hall, 1847, Pal. New York, vol. i, p. 192, pi. xlA, 



figs. 4a-k. 



Description. " Discoidal ; volutions in the same plane, about four, 

 rounded, slightly concave on the ventral side, gradually enlarging in size 

 towards the aperture, which is slightly expanded; surface marked by 

 lamellose irregular and oblique transverse striae or ridges, between and 

 upon which are finer lamellose striae, covering the outer surface, and 

 giving it a peculiar textural or netted appearance ; striae meeting in an 

 arch upon the back ; septa direct, or slightly undulated on the dorsal side ; 

 outer chamber large; siphuncle ventral." Hall, 1847. 



Only a small and imperfect example of this beautiful coiled cephalopod 

 has been noted in the Trenton fauna at the base of the Martinsburg shale. 

 So far as it goes this specimen agrees with the well-known Trocholites 

 ammonius of the New York Trenton. 



Occurrence. MARTINSBURG SHALE (Sinuites bed). Chambersburg, 

 Pennsylvania. Trenton limestone of New York and Kentucky. 



Collection. U. S. National Museum. 



