CARBONIFEROUS CEPHALOPODS. 343 



bolic (adult) stages. No tubercles were observed in Domatoceras umbilicatum, 

 although it was sufficiently well preserved to have shown them had they 

 existed. They might have been present in the earlier nealogic stages which 

 were not visible. In Centroceras the young whorl throughout the later 

 nealogic stages is tetragonal, but the sides are divergent, the abdomen being 

 broader than the dorsum. In this species during the same stages the sides 

 are nearly parallel or only slightly convergent, and the abdomen nearly equal 

 to or somewhat narrower than the dorsum. 



Centroceras (Temnocheilus) Scottense (sp. Worthen*) is a good example of 

 the genus Centroceras, having all the characteristic markings and form of 

 that genus. 



Domatoceras umbilicatum, n. s. 



Loc. Oswego, Kansas. Lower Coal Measures. 



Coll. Nat. Museum, by Dr. Newlon. 



Figs. 45-47, enlarged one-third. Fig. 47, natural size of living chamber 

 at first septum. 



This species reaches a considerable size, the specimen here described being 

 about 217 mm. in diameter. 



The living chamber is incomplete, and is a trifle over one-fourth of a 

 volution in length. The narrowing of the abdomen with increase of age is 

 very marked on the living chamber in this specimen. It measures 192 mm. 

 in length along the abdomen, 73 mm. in the abdomino-dorsal diameter at the 

 last septum, and about 52 mm. in the transverse diameter at the umbilical 

 shoulders, and 34 mm. near the venter. The sides of the whorls are flattened 

 and converge outwardly, so that the abdomen is considerably less in breadth 

 than the dorsum in the large full grown stage. There is a shallow impressed 

 zone upon the dorsum, which occupies about one-third of its width and is due 

 to the slight rotundity of the abdomen and the small amount of involution in 

 the colling of the whorls. ' The umbilical shoulders stand out abrupt and 

 broad, giving a depth to the wide umbilicus which is a marked characteristic. 

 The sutures have shallow ventral lateral lobes. The saddles at the umbilical 

 shoulders are broad and extend inwards to the edges of the impressed zone, 

 and then the sutures bend toward the apex, forming a shallow dorsal lobe. 

 There are no annular lobes in the centre of the dorsal sutures. The siphon 

 is above the centre and is apparently nummuloidal. At the diameter of 95 

 mm. the whorl has the following measurements: Abdomino-dorsal diameter, 

 41 mm.; transverse through the umbilical shoulders, 32 mm.; and breadth of 

 the abdomen was 25 mm. 



Domatoceras {Nautilus) complanatum, sp. Sow. Min. Cone, PI. 261, from 



*Geol. Surv. 111., VIII, PL 27, Fie. 3. 



