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and 21, have saddles on the venter with perhaps very slight ventral 

 lobes on either side of this, saddles at the lateral angles and faint 

 dorsal saddles. Schroder, also describes the same substages in 

 Estonioceras perforation and the sutures of the first whorl, but his 

 descriptive nomenclature is not clear and the text is consequently 

 not perfectly intelligible. Apparently the first whorl has broad 

 ventral saddles and nearly straight dorsal sutures with sometimes 

 very slight dorsal saddles. He states very distinctly, however, when 

 the whorls touch, at or near the end of the first whorl, that a decided 

 change takes place, the dorsal sutures acquiring well-marked dorsal 

 lobes. He also clearly states that in the uncoiled volutions this 

 dorsal lobe, although it persists, loses in height and breadth. 



In his descriptions of Lituites Muellaurei, of Dewitz, he makes 

 these statements clearer by saying that the dorsal and ventral sad- 

 dles possessed by the adult of this species are similar to the sutures 

 of the young species of Estoniceras perforatum and imperfectum, 

 which have sutures with ventral and dorsal saddles as figured by 

 him only on the venter of Estoniceras imperfectum. There is also 

 a shallow lobe developed in the middle of the dorsal saddle in 

 Estoniceras perforatum, which persists even in the gerontic stage. 

 After the lateral angles disappear in the ephebic stage, the saddles 

 and lobes are less prominent and become almost straight in the 

 more rounded volutions of the gerontic stage, but the approximate 

 return of the same outlines as are found in the paranepionic substage 

 is plainly visible, Figs. 17 and 18, PL vii. 



The lines of growth show a broad hyponomic sinus and lateral 

 crests which increase in prominence towards the dorsum, but 

 directly in the centre of that side there is a crest and on either side 

 of this shallow dorsal sinuses. There is, however, a dorsal sinus 

 which persists in the gerontic stage in the lines of growth of a 

 specimen figured by Schroder of Estonioceras heros* 



The aperture is wide in the ephebic stage, but evidently contracts 

 with the whorl in extreme age, as shown in Schroder's figure of 

 Estonioceras imperfectum, PI. iii, Fig. 2, b, and in the figures of 

 Estonioceras fiiangu/atum in this paper, PI. vii, and sometimes the 

 ventro-dorsal diameter may become longer than the transverse in 

 the paragerontic substage. This is, in part, a return to the early 

 proportions, since Schroder describes the apex of his Estonioceras 



* Op. cit. PI. v. 



