398 PALEONTOLOGY OF NEW YORK. 



Siphuncle near the convex ventral side, having a diameter at the septa 

 of three mm. where the tube measures thirty-five mm. 



Test not preserved. Surface marked by fine, sharp striaB of growth, which 

 make a distinct sinus on the ventral side. 



Internal mould essentially smooth, with the sutures slightly impressed. 



In three specimens the disc has a diameter of about 100 mm. each, and 

 the chamber of habitation has a greatest diameter of fifty mm. 



This species closely resembles T. eugenium, but differs in its more gibbous 

 form, less oblique sutures, and more curved and twisted chamber of habitation. 



A fact worthy of notice in connection with the Cyrtoceras, Gyroceras and 

 Trochoceras, of the Schoharie grit, is the much greater proportion of specimens 

 preserving surface characters than in Orthoceras from the same horizon. 

 Tins would seemingly indicate a much stronger test, with more decided surface 

 characters, than in the latter genus. 



Formation and locality. In the Schoharie grit, at Knox, Albany county, N. Y. 



Trochoceras Barrandei, n. sp. 



PLATE CXI, FIGS. 8-10. 



Shell large, nautiloid, gibbous, making about one dextral volution. Spire 

 depressed, not elevated above the upper lateral face of the grand chamber. 

 Transverse section* broadly oval or subcircular; lateral diameter apparently 

 the longer. Tube very rapidly enlarging from the apex to the aperture. 

 Apical angle about 22° in a specimen somewhat compressed. 



Chamber of habitation large, regularly expanding, with a capacity some- 

 what less than the volume of the air-chambers, curving in the direction of 

 the spiral axis. Crenulated band marked by obscure furrows, and several 

 involving lines at the base of the grand chamber. 



Air-chambers regular, deep, having a depth of twelve mm., measured on 

 the convex side of the tube, near the outer chamber, becoming gradually 

 more shallow toward the apex. The last one or two chambers, usually 

 somewhat shallower than the preceding. Septa smooth, with a concavity 



