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subcostal in aspect, but are somewhat exaggerated in Fig. n. In 

 the ephebic stages these subcostae are less prominent and do not 

 have any corresponding ridges on the cast, which is smooth. The 

 venter is also less elevated, the ventro-dorsal being less in proportion 

 to the transverse diameters and the whorl assumes the broad de- 

 pressed outline in section of this species. 



SCHROEDEROCERAS RAROSPIRA. 



Clymenia rarospira (pars) Eichw. (Leth. Rossica, PI. 1, Fig. la-b, 

 Fig. 3 ; not Fig. 2a-b, nor Fig. 6a, b, c*). 



This species has the aspect of Schroederoceras Saemanni on the 

 latter part of the second and third whorl, but the early part of the 

 same whorl in section is rounded and without a zone of impression. 

 The whorls increase faster by growth in the ventro-dorsal diameters 

 than in Saemanni. IfEichwald's figures can be relied upon the 

 species are distinct. The distribution of the prominent striae of the 

 neanic stage is instructive. They occupy all of the first whorl ex- 

 cept the apical part and are lost upon the last half of the second 

 whorl, persisting somewhat longer than in Saemanni or angulatum. 

 The siphuncle is depicted as very large, and according to the figure 

 is nearer the dorsum in the first and second whorl than it is in the 

 same age in Saemanni. The faster increase in dorso-ventral 

 diameters makes the adult somewhat larger in diameter of the coil 

 at the same age. 



The fact that the last volution is not free at the end shows proba- 

 bly that the specimen figured had not reached the gerontic stage of 

 degeneration. It is of course to be expected that some species of 

 Schroederoceras never become uncoiled, and this may be one of 

 these. Eichwald's Fig. ib also shows that the impressed zone is 

 deeper on the second whorl in the anephebic stage than it is sub- 

 sequently on the third whorl in the parephebic when a tendency 

 towards uncoiling begins to show itself in this way. The sutures 

 as shown in Figs. $a, b, c, are like those of Saemanni. 



Schroederoceras teres. 



Lit. teres, Eichw. (Si/, in Esthland, p. 105). 



Lit. teres, Dewitz (Schrif. physical-okonon. GeselL, Konigsberg, 



xx, PI. iv, Fig. 4). 

 Lit. teres, Schroeder {ibid., xxii, PI. ii, Fig. 2). 

 Discoc. teres, Schroeder (ibid., xxiii, p. 96). 



* See Trocholitoceras Eichwaldi. 



