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Estonioceras perforatum, Schroder (op. at., PL xxvi) ; PI. vii, 

 Figs. 9-12. 



Loc., Reval. 



The specimen, Fig. 10, PL vii, shows the dorsum of the parane- 

 pionic volution with the shell of the dorsum preserved. The dorsal 

 crest and dorsal sinuses of the lines of growth and in part the 

 sutures are visible. After this was drawn a part of the shell was 

 removed, exposing the dorsal sutures which are given in Fig. 12, 

 PL vii. These show the presence of a dorsal lobe as described 

 above with faint saddles, the remains of the younger dorsal saddle, 

 on either side of this. The ventral sutures have saddles at this 

 stage as may be seen by the outline of the whorl, but these were not 

 seen, although the ventral lobes on either side are plainly visible in 

 the side view of the paranepionic volution in Fig. 11. In the 

 metaneanic substage the dorsal lobe broadens and deepens in corre- 

 lation with the widening and deepening of the contact furrow, and 

 the lateral lobes appear then almost like saddles on the sides as in 

 Fig. 11 above in the outline of the only septum visible at this age in 

 this specimen. They are, however, still really slight aborad inflec- 

 tions or lobes. There is no true annular lobe at any stage. 



Fig. 9, PL vii, reproduced from Schroder's figures of Estonio- 

 ceras perforatum, shows that in this species in at least some varieties 

 the neanic stage probably does not acquire a contact furrow until it 

 strikes the metanepionic substage. 



The specimen figured is in collection of Mus. Comp. Zoology. 



Estonioceras biangulatum, n. sp. PL vii, Figs. 13-19. 



Loc, Breslau. 



The figures of this species show the large umbilical perforation 

 and digonal whorl of the paranepionic substage and neanic stages 

 seen from the side in the centre of Fig. 13, PL vii, and then from 

 the front with part of the outer whorl between the broken lines and 

 also the terminal part of the free whorl removed in Fig. 15. The 

 portion removed belongs to the ephebic stage, which in this species 

 has a digonal section. The lateral angles do not show rounding and 

 the lateral diameters continue to increase steadily and rapidly until 

 the anagerontic substage begins as the whorl becomes free. Then a 

 decisive decrease is noticeable in both of these characteristics. In 

 this specimen the transverse diameter through the middle of the 

 free volution without the shell, Fig. 17 and 18, was 42 mm., the 



