Clarke — The Naples Fauna. 



117 



definition of the peripheral band upon volutions where, in the normal, they 

 have totally disappeared. It is important to observe that Beech Kit's measure- 

 ments of the protoconch in this variety make it of considerably greater size 

 than we find to be the case in the normal Naples forms of the species. 

 According to that author, the transverse diameter of the protoconch is 

 1.06 mm.; we find it to be .77 mm. Most of our figures have been made 

 from isolated protoconchs, but whatever doubt might arise as to their form or 

 identity is dispelled by the adjoining figure, a section of a mature shell through 

 the protoconch. This figure has been reduced somewhat more than the others 



Figure 95. Tornoceras uniangulare. Section through the protoonch of an aiult shell, showing the modi- 

 fication of whorl section, the early increase and final decrease and total extinction of umbilication. x 18. 



on account of its size, but shows that the actual dimensions of the protoconch 

 are as elsewhere given. Representatives of this variety, compressum, are 

 common in the Styliola limestone in association with the normal. 



A laterally compressed shell from the horizon of the Hamilton group at 

 the Falls of the Ohio, Torn. Ohioense (figured without description under the 

 name Goniatites discoideiis, var. Ohioensis, Hall and Whitfield (Twenty-seventh 

 Annual Report N. Y. State Mus. Nat. Hist., pi. xiii, figs. 18, 19, 1873), may 

 prove on future investigation to be a similar variety. 



We may observe here the interesting fact, that the varietal differences 

 similar to these here noticed within the limits of Torn, uniangulare have 

 been recently defined by Gurich,* within the species Tom. circumfiexus 

 Sandb. ; namely, the varieties a/pplanata and incrassata. As the species 



* Op. cit. p. 338, pi. xiii, flgs. 5. 6. 



