624 
PLATE VY. 
Figs. t and 2. Zurystomites undatus (sp. Hall), Hyatt; Black River, Poland, 
Herkimer Co., N. Y.; Mus. Comp. Zodlogy, Walcott Coll. Natural size, show- 
ing large umbilical perforation and absence of dorsal furrow. A contact furrow 
is formed when the whorls come in contact in neanic stage. Siphuncle is too 
small and too near the venter in both inner whorls. (Fig. 3 is blank on this 
plate.) 
Figs. 21-25. Eurystomites rotundus, Hyatt, Quebec Group ; Fort Cassin, U. S. 
N. Mus., Walcott Coll. Enlargedslightly. Fig. 3, partly diagrammatic side view 
showing direction of section. Fig. 4, section. Fig. 5, section of nepionic somewhat 
nearer to that indicated in Fig. 3. Fig. 6 is about on that line and Fig. 7 is on 
the further side of it in the umbilical perforation. This series shows the large 
umbilical perforation and absence of impressed zone, until the whorls come into 
contact in the neanic stage. 
Figs. 4 and 5. Lurystomites (Naut.) Kelloggi (sp. Whitfield), Schréder; 
Loc., Fort Cassin, Quebec Group; Walcott Coll. U.S, Nat. Mus. Fig. 4, reduced 
one-third, showing the cast with the partly exfoliated rough shell in the gerontic 
stage and the restored gerontic free whorl which is in outline. The matrix was 
preserved so as to give the dorsal outline of this restored volution but not the 
sides or the venter. Fig. 5, section of the termination of the gerontic whorl. 
This is ideal so far as the sides and venter are concerned and may be too long 
ventrodorsally, but the dorsum is correct and shows the much narrowed but still 
persistent impressed zone. 
Fig. 6-10. Barrandeoceras (Naut.) tyrannum (sp. Barrande), Hyatt; Loc., 
Lochkov, Bohemia; Schary Coll. Mus. Comp. Zodlogy. 
Fig. 6, front view of part of the nepionic volution showing the cicatrix ana-, 
meta- and part of paranepionic substages, the constriction next to the cieatrix and 
the one just beyond this belongs to the ananepionic substage; the second is 
also seen in Fig. 7 a, the next constrictions seen in both of these figures 
belong to the metanepionic substage. There is apparently no hyponomic 
sinus in these two substages and its absence indicates the limits of the 
metanepionic substage. It is not plainly visible on this specimen until near the 
cracked line, which is really the septum of the living chamber. Fig. 7, side view, 
shell was not on the living chamber, but has been restored from other specimens, 
Suture is about as indicated with ventral and dorsal saddles and broad shallow 
lateral lobes. Figs. 6and 7 are X 4 diameters. Fig. 7a, an enlarged side view of 
apex of Fig. 7 to show true aspect of this part. Figs. 8, 9 and Io, similar views 
of another specimen showing identity of cicatrix and youngest substages in both 
shells. The markings are so delicate that they are easily obliterated and are 
necessarily much coarser in these drawings than in nature. Fig Io is enlarged 
about four diameters. 
Figs. 11-14. Barrandeoceras Sacheri (sp. Barrande) Hyatt; Loc., V. ch. 
Pridoli, Bohemia; Schary Coll., Mus. Comp. Zodlogy. Fig. 11 shows the large 
umbilical perforation, the sudden bending of the whorl at the end of the metane- 
pionic substage ; this occurs also in Fig. 7 and Fig. 9. Fig. 12,frontofsame. Fig. 
