350 GEOLOGICAL SURVEY OF TEXAS. 



EPHIPPIOCERAS. 



This genus has been sufficiently described in Genera of Fossil Cephalopods* 

 Ephippioceras divisum. 



Nautilus divisus, White and St. John, Descrip. Fossils, etc., Trans. Chicago 

 Acad. Sciences, I, p. 124. 



Loc. Kansas, near Oswego. Coll. Nat. Mus. from Dr. Newlon. 



Texas, in Coll. Geol. Survey, and from Kansas City, Mo., in Coll. Dr. New- 

 bery, N. Y. Lower Coal Measures. 



Fig. 52-54, one-third of the natural size. 



The fragment in hand is so much larger than any other specimen of this 

 genus yet found that its size alone- is characteristic. The length of the in- 

 complete living chamber is 195 mm. measured along the centre of the abdo- 

 men; the breadth of the same at the larger end is about 200 mm. through the 

 umbilical shoulders, and at the smaller end through the second septum about 

 118 mm. About two air chambers are left upon this fragment and a part of 

 a third. The whorl is kidney shaped in transverse section when looked at 

 from the surface of the septa. The abdomino-dorsal diameter on the side 



Fig. 54. 

 through the umbilical shoulder is 59 mm., while the same diameter taken 

 through the centre of the whorl is only 48 mm., the transverse diameter be- 

 ing, as noted above, 118 mm. Notwithstanding the large size of the living 

 chamber the form is quite as flattened as it is in the specimen of Ephip. 

 Ulobatum figured by DeKoninck in his Calcaire Carbonifere,f and there is 

 also a similar depressed area, or broad shallow zone, running longitudinally 

 along the venter. It is probable that no other species of nautiloid increases 

 laterally more rapidly by growth than this ' one. The transverse measure- 

 ments as given above are so large and the aspect from behind is such as to 

 lead people to speak of these fossils as petrified skulls. The dorsal impression 



*Op. cit., p. 290. 



fAnn. du Mus. Roy. de Belgique, II, PI. 9, Fig. 1. 



