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Plate V. 



Figs. I and 2. Eurysto?nites undatus (sp. Hall), Hyatt; Black River, Poland, 

 Herkimer Co., N. Y.; Mus. Comp. Zoology, 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 rotundas, Hyatt, Quebec Group; Fort Cassin,U. S. 

 N. Mus., Walcott Coll. Enlarged slightly. 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. Eurystomites (Naut.) Kelloggi (sp, Whitfield), Schroder; 

 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 (Xaut.) tyrannum (sp. Barrande), Hyatt; Loc, 

 Lochkov, Bohemia; Schary Coll. Mus. Comp. Zoology. 



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 cicatrix 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. 6 and 7 are X 4 diameters. Fig. 7 a, an enlarged side view of 

 apex of Fig. 7 to show true aspect of this part. Figs. 8, 9 and 10, 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 10 is enlarged 

 about four diameters. 



Figs. 11-14. Barrandeoceras Sacheri (sp. Barrande) Hyatt; Loc, V. ch. 

 Pridoli, Bohemia; Schary Coll., Mus. Comp. Zoology. Fig. 1 1 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, front of same. Fig. 



