Raymond : Fauna of Upper Devonian of Montana. 1 51 



venter. Some of these ribs point slightly forward, others a little 

 backward. The ribs become gradually further apart on each whorl, 

 until on the body whorl they are quite distant from each other. 

 They do not bear any fixed relation to the cameras, for, as may be 

 seen on the figures, a rib may be between the septa, or may be cut in 

 any direction by a septum. The dorsum is slightly concave and is 

 frequently marked by a revolving line showing the position of the 

 siphuncle. As shown by the figures, the suture is very simple. 



This species is more closely related to Platyclymenia anmilata 

 (Munster) than to any other described species, and differs from it 

 principally in the more depressed section of the whorls and the 

 coarser ribs. A copy of Freeh's figure of Platyclymenia annulata 

 from his monograph ^^Uber devonische Ammoneen ; Beitrdge zur Palli- 

 ontologie und Geologie Osterreich-Ungarns und des Orients,'''' Band 

 XIV, Heft I und 2, 1902, t. 2, figs. 6<r-6r, is here introduced for 

 comparison (Plate VII, figure 8). 



Locality. — This species is found in the red shale, the green shale, 

 arid the limestone of the Upper Devonian at Three Forks, Montana. 



Platyclymenia polypleura sp. nov. 



(Plate VII, FIGURES 4-6.) 



Description. — This species may be described by saying that it dif- 

 fers from the preceding in its somewhat smaller size, shallower cam- 

 eras, and, principally, in the much more numerous and finer ribs 

 which ornament the surface. The ribs of the body 

 whorl, instead of becoming very strong and distant, 

 become weaker and more numerous, and extend 

 further on the venter. 



This species bears much the same relation to 

 Platyclymenia ameiHcana that the variety Platycly- ^ „, 



menia annulata densicosta Freeh does to Platycly me- dymenia polypUu- 

 nia anmdata (Munster). In surface ornamentation ;-<? Raymond, 

 our species is much like the German variety of annu- Outline drawing 

 lata described by Freeh, but the whorl section is of the type to show 

 i-rr T r. , , t 11 • • sutures. Natural 



very dinerent. In P. polypleura the whorl section is 



depressed, with a rounded venter, while in P. anfiii- 

 lata densicosta it is slightly compressed and has a distinctly flattened 

 venter. (See figure 7, plate VII, which is copied from figure 5, plate 

 2, of Freeh's " Ul?er devo?tische Anunoneen.'") 



