84 NEW YORK STATE MUSEUM 



kionocekas Hyatt. 1883 

 Kionoceras darwini Billings (sp.) 



Plate 10, fig. 22; plate 11, fig. 6; plate 12, fig. 1-8 



Orthoceras darwini Billings, Paleozoic Fossils. 1862. 1 : 161 (not figured) 



Cyrtoceras myrice Hall & Whitfield, Geol. Sur. Ohio. 1875. v. 2, pt 2, Pale- 

 ontology p. 149, pi. 8, fig. 9 



Orthoceras darwini Whiteaves, Paleozoic Fossils. 1884. v. 3, pt 1, p. 38, pi. 6, 

 fig. 2, 2a 



Cyrtoceras myrice Whiteaves, Paleozoic Fossils. 1884. v. 3, pt 1, p. 39, pi. 6, 



fig- 3, 3a 



Orthoceras darwini Foord, Cat. Fossil Cephal. British Museum. 1888. pt 1, 

 p. 76, fig. 8 



Orthoceras darwini Whiteaves, Paleozoic Fossils. 1895. v - 3> P* 2 > P- I0 ° 

 Among the Rochester specimens of this species is one which is 

 excellently preserved and shows the surface features probably better 

 than any which have been recorded. There are sharp, angular, longi- 

 tudinal ridges, between each pair of which normally lies a smaller 

 ridge. These ridges of the first and second order are separated by equal 

 furrows. Concentric lineation does not appear on this specimen but is 

 shown on the later growth of a larger individual. Toward the apical end 

 of the shell are quite well marked transverse annulations. These, as in 

 many other species of this generic type, are completely obscured in later 

 growth. The gentle cyrtoceran flexure of the cone is clearly indicated in 

 the best of the specimens. The sipho is subcentral and the section is nearly 

 circular, with the concave side slightly flattened. 



No examples of this pretty and characteristic species have been 

 obtained in the upper Shelby bed, but the lower dolomite has fur- 

 nished a number of well preserved specimens, two of which are remarkable 

 for their dimensions, which indicate a size considerably larger than hitherto 

 recorded. One of these is preserved as a mold of the exterior and attains 

 a length of 158 mm, with both ends imperfect. This retains the same 

 slight curvature exhibited by the smaller specimens. Another is a cast of 

 the interior of the living chamber and of 10 septa, which shows but very 



