144 ANNALS NEW YORK ACADEMY OF SCIENCES 



compressed and seems to show a structure down one side suggesting a marginal 

 siphuncle. 



Horizon and locality: Wewoka formation; Wewoka quadrangle, Okla. 



Protocycloceras ? rushense var. crebricinctum var. nov. 



Two specimens, though resembling P. ? rushense, are distinguished by having 

 the aunulations more closely arranged and somewhat alternating. The cross- 

 section is elliptical as in that species, but there is an acceleration of expansion 

 which produces a flaring shape toward the aperture. The recurrence of this 

 latter character, which is found to a marked degree in one of the species of 

 Orthoceras, is noteworthy and seems to bring its importance somewhat into 

 doubt. Its significance is entirely unknown. 



One of the specimens shows the surface to be marked by fine, subequal, 

 somewhat wavy, thread-like, transverse lira?. 



Horizon and locality: Wewoka formation; Wewoka quadrangle, Okla. 



Coloceras liratum sp. nov. 



Shell small, the largest specimen seen measuring 34 mm. in the plane of 

 revolution. Shape subglobose. Cross-section sublunate, somewhat gibbous at 

 the sides. Surface rather regularly curved over the venter ana sides, abruptly 

 rounded inward at the umbilicus, forming two not very well-defined umbilical 

 zones, the direction of which is nearly horizontal. At maturity, the section is 

 about twice as wide as high. In mature specimens, the median line of the 

 venter is broadly and faintly impressed. The rate of increase is rapid and the 

 depressed zone narrow, considerably less thau one half the width of the pre- 

 ceding whorl. The umbilicus is rather small and deep. 



The surface is marked at the sides by fine revolving lira?, separated by wide, 

 fiat interspaces. These extend from the umbilical zone over the subangular 

 shoulder onto the extreme sides of the venter. The revolving lirse are crossed 

 in some cases by much more closely arranged transverse ones which make fine 

 crenulations as they surmount them. The entire surface of the immature 

 stages seems to be thus cancellated, but only a band on the sides of the mature 

 shell, while on the oldest specimens and some others, the transverse markings 

 cannot be seen. The ventral surface is crossed by fine, incremental stria?, 

 which indicate a deep, subangular V-shaped sinus, whose sides are nearly 

 straight over the median portion but curve gracefully outward with increasing 

 rapidity toward the sides. In one specimen, the stria? are so arranged that 

 every seventh or eighth is stronger than the others, which cross the slightly 

 elevated spaces between in crowded though regular order. 



The septa are rather far apart, about G mm. along the median line in a 

 mature specimen. They are nearly straight except for a slight sinuosity across 

 the venter caused by the shallow ventral lobe and a pair of obscure saddles. 

 The siphunele appears to be situated below the center (dorsad) but it is not 

 weH shown. 



