238 NORTH AMERICAN INDEX FOSSILS. 



Tubes irregularly annulated, often united; length one half inch 

 or more; rings about 20; diameter at mouth one tenth inch. 

 Cincinnatian of Ohio. 



13. C. gregarius Nicholson. Ordovicic. 

 Smaller than preceding, more closely crowded; diameter one 



twenty- fourth inch; attached to shells. 

 Cincinnatian of Ohio. 



IV. CoRNULTTES Schlotheim. 



Tube trumpet-shaped, gently tapering, flexuous, the small end 

 usually bent ; the tube closed at its lower end and either wholly or 

 in part adhering to other objects; it at times attains a length of 

 three or four inches ; walls thick, cellular, composed of imbricating 

 rings; surface ornamented with annulations and longitudinal 

 striae ; interior presenting a succession of ring-like constrictions, 

 giving to the internal mold a step-like appearance. Ordovicic- 

 Devonic. 



14. C. proprius Hall. Siluric. 

 Rapidly enlarging; adhering when young and strongly and sub- 

 regularly annulated; adult (up to three inches in length) with 

 irregular lamellose growth lines, and fine longitudinal striae; 

 structure of tube vesiculose. 



Niagaran of Indiana, Tennessee, etc. 



15. C. bellistriatus Hall. (Fig. 1523.) Siluric. 



^l^-u 



d 



Fig. 1523. Cornulites bellistriatus. (After Hall.) 



W^ll thick; annulations scarcely marked at base, less strongly 

 and irregularly marked in upper portion and more regular than in 

 C. proprius; fine longitudinal striae throughout; probably only a 

 variety of the preceding. 



