716 



Report of the State Geologist. 



writer already has had occasion to' observe the round section of the basal part 

 of larger specimens before this material was found (see PI. I, figs. 3 and 4), 

 and the concentric furrows on the apertures of flattened specimens, which 

 were mentioned above (cf. PI. IV, fig. 20), point to the same fact. 



It may be concluded from these observations that the young shell of 

 Conularia gracilis consisted not only of the thin sculptured surface layer but 

 also of a thicker carbonaceous interior layer. The interior surface of the 

 living chamber, formed by this latter, was smooth. This can be seen 

 wherever the cast only of the shell is preserved, as for instance in the original 

 of figure 40, at h. The cast consists of four smooth faces extended between 

 the marginal grooves. 



The uncompressed specimens show further that the young shells were, 

 in fact, much more slender than the compressed fossils would suggest. They 

 often approached at the basal end more to a cylindrical than a conical shape, 

 an observation which is illustrated in the above mentioned figures of Plate I 

 (figs. 3 and 4). The latter figure also shows well the gradual change of 

 the cylindrical young shell into the pyramidal form by the marginal grooves 

 becoming more prominent. There is no doubt that the marginal grooves were 

 present in the incipient shell, for this is proved by the originals of figures 5, 

 7, 10, etc. (PI. IV), but they were only part of the superficial layer, as shown 

 by the specimens belonging to figures 36 and 38, and became important only 

 in the thinner later part of the shell. 



The writer has added to these illustrations that of a fragment of a shell 

 which plainly shows a convex segment at the apex (cf. fig. 39). It naturally 

 can not be decided from a single specimen* whether this shell accidentally 

 broke at the segment or whether we see the result of a discarding of the basal 

 appendage by the adolescent animal. It is worth mentioning in regard to the 

 latter possibility that the writer made only one other observation which 

 might indicate the existence of septa in Conularia gracilis, namely the above 

 mentioned constrictions of the original of figure 35, Plate IV. 



Finally, a reproduction of the type of Sphenotkallus angustifolius, Hall, has 

 been added in figure 40, in order to indicate the traces of basal appendages, 

 which are perceptible, as well as two young shells attached to a larger one at 

 a. A part which is of interest in regard to the conception of the shape of 

 Conularia is marked />. The upper face of the pyramid is here broken away, 

 whereby the crushed lateral faces and the opposite lower face are laid open. 

 The section of the cast is broadly rectangular. 



* The apes of the original of Plate II, Hgurc B, is not distinct enough to l)e of accour.i. 



