635 
PATE PSX, 
Figs. 1-3. Leripetoceras (Naut.) Frieslebent (sp. Geinitz); Loc., Tunstall 
Hill, England; Mus. Comp. Zoél.; Dyas. Natural size. Fig. I shows the 
section through the apex of the conch, the ananeanic volution below and a 
later age of the neanic stage above. Fig. 2, the cut has passed through the um- 
bilical perforation, the metanepionic above this and the paranepionic below; 
above the metanepionic is the paraneanic or anephebic substage. Fig. 3, the 
cut has approached the farther side of the umbilical perforation and shows an 
older age of the metanepionic and a younger age of the paranepionic with a deeper 
and better defined dorsal furrow than in Fig. 2. 
Figs. 4-8. Syringoceras (Naut.) granulosostriatus, after Mojsisovic’s MZedzt. 
Triaspr., Pl. \xxxii, Figs. 7 and g, Trias. Figs. 4 and 5, nepionic stage enlarged. 
Fig. 8, more enlarged view of apex, with a cicatrix. Figs. 6 and 7, paranepionic 
and ananeanic substage with longitudinal striations and beginning of impressed 
zone after contact. 
Figs. 9-12. Syringoceras (Naut.) Linearis, after Laube; Fauna St. Cassian 
Denksch. Akad, Wien, 1869, Pl. xxxvi, Trias, Fig. 12, natural size. Figs. 9-11, 
enlarged. Fig. 10, to show more accurately shape of apex. All show nepionic 
stage and development same as in granzlosostriatus. 
Figs. 13 and 14. Digonioceras (Naut.) excavatum, after D’Orbigny, Zerr. 
Furass., Pl. xxx, Lias. These show the nep onic stage with an impressed zone 
existing before contact, also the annular lobe. 
Figs. 15 and 16. Cesoceras (Naut.) intermedium (sp. Sow.), Balingen, De 
Koninck Coll. Mus. Comp. Zo6l.; Middle Lias. Slightly enlarged. These show the 
large umbilical perforation and sutures, the paranepionic and ananeanic substages. 
The dorsal furrow is present only in the paranepionic substage and the beginning 
of the contact furrow is shown also in the shaded area on the dorsum of Fig. 16. 
Figs. 17 and 18. Cexoceras (Naut.) intermedius (?) (sp. Sow.), after Bar- 
rande and Hyatt, Syst. Sz/., Pl. ececlxxxix, Fig. 7; D’Orbigny Coll. Jarden des 
Plantes; Middle Lias. These show the ana- and metanepionic substages with 
cicatrix and sutures, but no impressed zone. 
Figs. 19-21. Digonzoceras sp. ? (similar to excavatus), Balingen; De Koninck 
Coll., Mus. Comp. Zo6l.; Middle Lias. Natural size. Fig. 19 shows sutures, 
ete., of paranepionic substage. Fig. 20 gives outline of same from dorsum with 
the dorsal furrow in the paranepionic, the upper outline of this figure is incorrect 
since the dorsal furrow begins immediately below this. Fig. 21 gives this out- 
line correctly, it being the last of the ananepionic substage at the second suture; 
in Fig. 21, the venter is placed uppermost for comparison with Fig, 20. 
Figs. 22-27. Cenoceras lineatum (sp. Sow.), Bayeux; Coll. Duval, Mus. 
Comp. Zodlogy ; Inferior Ool. Fig. 22, natural siz2, showing umbilical per- 
foration, metanepionic substage below perforation and paranepionic above this, 
the neanic stage being below the metanepionic volution. The dorsal furrow 
is well developed in the paranepionic substage. Fig. 23, the reverse of the two 
upper sections of Fig. 22. 
Figs. 24 and 25, views of another specimen, showing the nepionic stage, en- 
larged 3 diameters, showing the position of the siphuncle ventrad of centre and 
