222 



Fui. 131A. Treinatospira gibboaa. Dorsal, ventral, cardinal, profile, and front views 

 of a characteristic individual (from Hall.) 



sinus; zio-zap; lines, formed bv concentric lamellfe of growth, 

 in crossin<!,' ])lications: <;rannlose character of surface. 



Found in the Hamilton ^rouj), at Eighteen Mile Creek. 

 (Coll. Am. Mus. Nat. Hist. New York.) 



Genus NUCLEOSPIRA. Hall. 



- [Ety. : Nucleus, kernel ; sjrini, spire.] 



(lS.-)9: 12th Rep't N. Y. State Cab. Nat. Hist., p. 24. 1893: Pal. N. Y., 

 Vol. VIII., Pt. II., p. 142.) 



Shells usually small: sub-circular in outline; biconvex, 

 with the valves nearly equal, often gibbous. A small area is 

 present on the pedicle valve, but it is obscured by the incurv- 

 ature of the beak. Strong teeth, and a median septum occur 

 in the |)edicle valve. Surface in perfect specimens covered 

 with numerous long, slender spines, smooth in worn or mac- 

 erated specimens. Brachidium a double spire. 



Nugleospira concinna. Hall. (Fig. 132.) (Pal. N. Y., 

 Vol. IV., p. 270, PI. XIV.) 



Distinguishing Cliaracters. — Nearly circular outline; sub- 

 erpially convex valves; median septum (or its impression in 

 the internal mold): surface spines. 



fK'/'f't 



yi/U 



i 



Fig. 1.32. Nucleospira concinna. Dorsal, ventral, profile, and cardinal views ; beak of 

 pedicle valve enlarged, showing teeth and false area : portion of surface enlarged, showing 

 spines : cardinal process of brachial valve enlarged (from Hall). 



