523 
FSTONIOCERAS PERFORATUM, Schroder (of. cc¢., Pl. xxvi); Pl. vii, 
Figs. 9-12. 
ioe: ‘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 Schréder’s figures of /s/onco- 
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. Zodlogy. 
ESTONIOCERAS BIANGULATUM, n. sp. _ PI. 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 adigonal 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 
