158 THE DEVONIAN OF MISSOURI. 



Siphuncle small, subcentral, only observed at the septa, where its diameter is one 

 mm., the tube having a diameter of fifteen mm. at the same point. 



Test thin, usually showing a thickness of .2 mm.; sometimes it is considerably 

 stronger over the anterior portion of the chamber of habitation. Surface marked by 

 very fine, irregular, lamellose striae of growth. Some of the specimens show longitudinal 

 striae, and more rarely very fine, filiform, longitudinal markings." 



Remarks — -Fragments from Missouri agree with 0. subulatum Hall, but as the 



iving chamber is not present and a constriction in the living chamber is the main 



difference between this species and 0. constrictum Vanuxemi the reference is uncertain. 



The location of the siphuncle has not been positively determined and the larger specimens 



may belong to 0. exile Hall. 



Occurrence — Grand Tower limestone of Little Saline Creek. 



Family Rhadinoceratidae 

 Genus Nephriticeras Hyatt 



Nephriticeras 



Plate 37, figure 8, 9; plate 38, figure 4. 



Fragmentary specimens of two species of this genus from the Grand Tower lime- 

 'stone are in the collections of Walker Museum. 



Suborder CYRTOCHOANITES 



Family Phragmoceratidae 



Genus Gomphoceras Sowerby 



Gomphoceras grandtowerensis n. sp. 

 Plate 37, figures 6 and 7. 



Description — Shell of medium size, nearly straight; transverse section oval; place 

 of greatest diameter the chamber adjoining the living chamber. Living chamber with 

 the sides convex and contracting gradually to a place 22 mm. from the base. From 

 this constricted band outward the sides are nearly straight. The aperture is narrowly 

 oval. The average depth of the air chambers is 4 mm. 14 chambers are preserved in 

 the type specimen and there is little difference in their depth. ' The septae are slightly 

 curved backward on the less convex surfaces. Siphuncle not observed. The specimen 

 is remarkable for its symmetry. 



Occurrence — Grand Tower limestone of Little Saline Creek. 



Gomphoceras hyatti Whitfield 



Plate 38, figure 1. 



1882. Gomphoceras Hyatti Whitfield, N. Y. Acad. Aci., 2nd Ann. Report, p. 206. 

 1893. Gomphoceras Hyatti Whitfield, Ohio Geol. Surv. , vol. VII, pp. 427-428 pi. 4, 



fig. 1; pi .5, figs. 1-2. 

 1910. Poterioceras hyatti Grabau and Shimer North American Index Fossils, II, p. 

 128; fig. 1374 a, b. 

 Whitfield's description — "Shell large and robust, slightly arcuate throughout, but 

 more strongly curved below than in the upper part; somewhat rapidly expanding from 

 below upward to near the middle of the outer chamber, where it is suddenly contracted 

 to the aperture, and on the lateral margins again slightly expanding. The rate of increase 

 in diameter, as compared with the increased length is about as one and two, when meas- 



