320 S. WELLER FAUNA. OF THE FERN GLEN FORMATION 



The dimensions of two individuals are: Extreme length of the shell, 

 34 millimeters and 27.5 millimeters; length of aperture, 22 millimeters 

 and 19 millimeters; width of aperture, 25 millimeters and 21 milli- 

 meters; greatest height of shell, 16 millimeters and 15 millimeters. 



Remarks. — This is a rather common species in the Fern Glen fauna, 

 and like all members of the genus it exhibits a considerable range of 

 variation because of the sedentary habits of growth. One of the most 

 noticeable variations is in the curvature of the apex of the shell. The 

 normal condition of the apex is as has been described above, but exam- 

 ples are occasionally met with in which the apex is not coiled at all, the 

 shell being a more or less oblique or curved conical shell, such a form 

 probably being assumed from the effect of gravity during the growth of 

 the shell, due to the position of the shell during life. 



CEPHALOPODA 

 ORTHOCERAS sp. undet. 



Fragments of a species of Orthoceras are sometimes met with in the 

 Fern Glen fauna. In their present condition they rarely retain more 

 than two or three chambers and are all crushed so as to have a subellip- 

 tical outline, although they were probably originally circular in cross- 

 section. No characters which may be used for specific determination 

 are preserved. 



CYRTOCERAS ? sp. undet. 



A single fragment of a curved cephalopod shell has come under obser- 

 vation. Only three chambers are preserved, and these imperfectly. 

 The shell is subelliptical in cross-section, the larger diameter being trans- 

 verse to the plane of curvature; the siphuncle is situated excentrically 

 toward the ventral side. 



ARTHROPODA 



TRILOBITA 

 PROETUS FERNGLENENSIS n. sp. 



Plate 15, figures 2022 



Description. — Entire body subovate in outline, strongly convex, the 

 greatest width about five-eighths of the total length. Cephalon sub- 

 crescentic, the genal angles produced into conspicuous spines, the mar- 

 ginal border broadly rounded, marked by about four narrow costal sub- 

 parallel with the outer margin ; glabella strongly convex, well defined by 

 the dorsal furrows, slightly protuberant in front, the lateral outlines a 



