Maryland Geological Survey 319 



oval or subcircular; point of greatest gibbosity posterior to the middle of 

 the living-chamber ; apical angle about 30°. Living-chamber gibbous, with 

 the sides convex, and sloping gradually to the aperture; crenulated band 

 not well defined, but the markings are preserved over the cast of the walls 

 of the air-chambers as broad, shallow, longitudinal furrows. Air-chambers 

 regular, having a depth of about 4 mm.; septa smooth, moderately con- 

 cave; sutures, in uncompressed specimens, straight and horizontal. Test 

 and surface markings unknown; internal mold smootli, with the excep- 

 tion of the crenulations over the walls of the air-chambers; sutures but 

 slightly impressed. A fragment embracing a portion of the living- 

 chamber, with five attached air-chambers, has a length of 50 mm.; of 

 which about 30 mm. pertain to the grand chamber, which has a greatest 

 transverse diameter of 40 mm." 



The Maryland specimen is apparently part of a living-chamber with a 

 length of about 72 mm. and width of 58 mm., which is slightly arcuate, 

 quite convex, sides sloping and siphuncle eccentric. 



Occurrence. — Eomney Formation, Hamilton Member. Western 

 Maryland. 



Collection. — Maryland Geological Survey. 



Order AMMONOIDEA 



Suborder MICROCAMPYLI 



Family BACTRITIDAE 



Genus BACTRITES Sandberger 



Bactrites aciculatus (Hall) 

 Plate XLII, Fig. 4 



Dentalium aciculatum Hall, 1860, Thirteenth Rep. N. Y. State Cab. Nat. Hist., 



p. 107. 

 Coleolus (Dentalium (?)) aciculatum Hall, 1879, Pal. N. Y., vol. v, pt. il, p. 



190, pi. xxxii A, figs. 17, 18. 



Description. — " Form slender, elongate, cylindrical, tubular, very 

 gradually attenuating from the base; surface striated (?). The speci- 

 mens under examination are several fragments of longer tubes, but there 



