•>■>•) 





In.. 181A. Trematospira gibbosa. Dorsal, central, cardinal, profile, and front views 

 of a characteristic individual (from Hall.) 



sinus: zigzag lines, formed by concentric lamellae of growth, 

 in crossing plications; granulose character of surface. 



Found in the Bamilton group, at Eighteen Mile Creek. 

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



Gems NUCLEOSPIRA. Hall. 



[Ety. : Nudeits, kernel ; spira, spire.] 



(1859: 12th Kept X. V. State Cab. Xat. Hist., p. 24. 1893: Pal. X. 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- 

 ,i t ure of the beak. Strong teeth, and a median septum occur 

 in the pedicle valve. Surface in perfect specimens covered 

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

 erated specimens. Brachidium a double spire. 



Nucleospira coNCiNNA. Hall. (Fig. 132.) (Pal. X. Y., 

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



Distinguishing Characters.— Nearly circular outline; sub- 

 equally convex valves: median septum (or its impression in 

 the internal mold): surface spines. 



<' A 







fill, 



'__:__ 



182 Nudeospira concinna. Dorsal, ventral, profile, and cardinal views: beak of 

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

 spin."- : cardinal process "f brachial valve enlarged (from Hall). 



