CARBONIFEROUS CEPHALOPODS. 



333 



Fie-. 27. 



Fig. 28. 



Fig. 29. 



Temnocheilus crassus, n. s. 



Loc. near Oswego, Kansas. 



Carboniferous. Coll. National Museum. 



Figs. 27-29. Magnified one-third. 



This species is represented only by a fragment, but the characteristics are 

 so peculiar that there is apparently little doubt of its being the representative 

 of a distinct form. 



The sides are convex and do not converge towards the umbilici so abruptly 

 as in most forms of this genus. They are covered by numerous well defined 

 straight pilse, terminating in small nodes at the edges of the abdomen. The 

 abdomen is convex, with a narrow slightly depressed zone along the centre. 

 The shell is ornamented by prominent striae of growth, and at regular inter- 

 vals one of these is more prominent than the neighboring striations, showing 

 frequent short arrests of growth. These striae are straight upon the sides, 

 but upon the abdomen bend suddenly posteriorly, forming wide sinuses of 

 great depth; doubtless the aperture was similar. The sutures are almost 

 straight on the sides and have a very broad and slight ventral lobe. Si- 

 phuncle unknown. 



This shell is very similar to Nautilus falcatus, L. de C. Sowerby,* in so far as 

 they both have ribs. The Coalbrookdale specimen, however, has no tubercles, 

 or at least none are given, and the sides of the whorl are figured as concave. 

 Naut. Nikitini, Tzwetaev,f is also very similar, but the ribs are less numerous 

 and the sutures quite different. Nikitini has saddles and lobes as in Taino- 

 ceras. Living chambers were not observed. Position of siphuncle is un- 

 known. 



Figs. 27 and 28 show the fragment, and Fig. 29 is therefore in part a 

 restoration. 



* Prestwich, Geol. Coalbrookdale, Trans. Geol. Soc. London, V, PI. 40. 

 f Op. cat, PI. 1, Fig. 5. 



