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tained. The aperture was not very plainly discernible, but was ap- 

 proximately as given in the figure. 



The ephebic stage has raised lines or bands of growth straighter 

 on the sides than in the gerontic stage, which has evidently begun 

 on the last whorl. This has moderately heavy ridges which are re- 

 flected on the cast of the living chamber. 



It is separable from Schroederoceras Eatoni by the broad whorls 

 of the young and the near approximation of the siphuncle to the 

 dorsum in the neanic stage. 



TROCHOLITOCERAS (?) ElCHWALDI. 



Clymenia rarospira, Eichw. {Leth. Rossica, PL 1, Fig. 2, a, b, c, 

 and 6, a, b, c ; not Fig. 1, a-b, and 3). 



The descriptions and figures of Eichwald show conclusively that 

 this is widely different from Schroederoceras rarospira and is nearer 

 to true Trocholites. The form of the whorls in the young, the slow 

 rate of increase in the dorso-ventral diameters, the rotundity of the 

 sides and abdomen in the young and even in the full-grown whorls, 

 the small diameter and close approximation of the siphuncle to the 

 dorsum, make this shell very like a species of Trocholites. 



On the other hand, the sutures are more sinuous, having deeper 

 ventral and lateral lobes than are common in that genus. The 

 living chambers are less than one-fourth of a volution in length, with 

 the lateral crests of the aperture most prominent about the centre of 

 the lateral aspect. 



The question of affinity can of course only be definitely settled 

 after the development of the siphuncle in the apex of the conch has 

 been studied. The appearance of the umbilicus, as shown in Fig 6 

 of Eichwald, is similar to that of other species of this genus, but this 

 of course may be due to erroneous draughting. 



Trocholites. 



This genus has been fully described and correctly defined by 

 Schroder,* and the following description is largely taken from his 

 work and adapted to the needs of this work. The shell of the ne- 

 pionic stage, as first shown by Holm,f is so closely coiled that no 

 umbilical perforation is externally visible. Observations of two 

 young specimens of T. described below have, however, shown the 



* " Unters. ub. sil. Ceph.," Pal. AM., Dames et Kayser. N. F. (current Vol. v), heft 4. 

 f "Sil. Ceph.," Pal. Abh., Dames et Kayser, iii, PL v, Figs. 9, 10 and 11. 



