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Fig. 43. Cranoceras (Cyrl.) lineatum (sp. De Verneuil), Hyatt; Devonian, 

 Pelm near Gerolstein ; Mus. Comp. Zoology, Schultze Coll. Fig. 43, outline to 

 show the impressed zone which seems to appear in this cyrtoceran form in corre- 

 lation with the nephritic outline independently of contact. 



Plate IX. 



Figs. 1 and 2. Thoracoceras (Cyrl.) puzosianum after De Koninck, Calc. 

 Carbon. PL xxxiii, Figs. 10 and 1 1, to show in an adult of arcuate form the same or- 

 namentation and form that are also present in the young of the more highly 

 ornamented species like Thoracoceras canaliculatn?n and the young of many 

 nautilian forms. See Figs. H-13 of Vestinautilus Konincki. 



Figs. 3 and 4. Thoracoceras (Gyrt.) canaliculatum, after De Koninck, ibid., 

 PI. xxxiii, Fig. 9, to show the spinous character of the ornamentation produced by 

 prominent lines of growth in crossing over the longitudinal ridges ; also for com- 

 parison with the young of Triboloceras, Vestinautilus, Rineceras, etc. 



Figs. 5-13. Vestinautilus (IVaut.) Konincki (sp. De Koninck), Hyatt; Figs. 

 5-8, after De Koninck, ibid., PI. xxx, Fig. 1 ; Figs. 11-13, Hyatt, Emb. 

 Ceph., PI. 4; Figs. 9 and 10 original. This series shows ontogeny of this spe- 

 cies. Figs. 9 and 10, nepionic stage and ananeanic substage. Figs. 11-13, ana- 

 and metanepionic with rounded whorl and cyrtoceran form and ornaments like 

 T. puzosianum ; the roughened spinous ornaments come in later in the parane- 

 pionic substage. The limit of the paranepionic is shown in Fig. 9, the ananeanic 

 begins in last half of the first volution when the inner longitudinal ridges cease 

 on the sides. Compare abdomen with ephebic stage of Triboloceras, Fig. 15. 

 The ephebic stage begins near the end of the first half of the second volution 

 when the gibbous lace and the lateral dorsal flutes or faces begin to appear in the 

 zone of involution as in Fig. 7. The anagerontic substage is shown in the loss 

 of the ornaments in Figs. 5 and 6, and also in the diminution of the hollow cen- 

 tral ventral zone and tendency of the abdomen to become rounded. 



Figs. 14 and 15. Triboloceras (Gyroc") intemiedium, after De Koninck, 

 ibid., PI. xxxiii, Fig. 4. 



Figs. 16-19. Vestinautilus (JVaut.) pinguis, after De Koninck, ibid., PL 

 xxx, Fig. 6 a-c, and Fig. 7 a, b. Figs. 18 and 19 show the anephebic substage 

 with spinous ornaments, the loss of these in the succeeding part of the ephebic 

 stage and the replacement of the ventral hollow zone, which is present in the 

 nepionic stage of this species, by a gibbous face like that of the gerontic stage of 

 Konincki. Figs. 16 and 17 show the parephebic substage and anagerontic 

 substage, the latter occurring through loss of the lateral fluted faces as in Fig. 5, 

 of Konincki. In the succeeding gerontic substages the whorl loses its angularity. 



Figs. 20 and 21. Rineceras (Gyroc ) tessellatum, after De Koninck, ibid., 

 PL xxxiii, Fig. 5, 5 a. 



Figs. 24 and 25. Lispoceras (JVaut.) sulciferum, after De Koninck, ibid., 

 PL xxxi, Fig. 7 a, b. 



Figs. 26 and 27. Phacoceras (Nazit.) oxystomum, after De Koninck, ibid., 

 PL xvii, Fig. 3. 



