The Quarterly journal of the Geological Society of London . receding-septa. These facts run counter to, the views of Eiefstahl ^supported by Buckman ^; and, along with the observations ofWilley (1902) upon Xautihis, they furnish further support, ifsuch be needed, for those of Bather ^ and Appellof.^ According toRiefstahl, the last septum was formed in contact with the previousone, and became separated by the growth of the interveningshell-wall. He based his view upon the microscopical studyof tlie sepion. This, however, is so highly modified that it wouldnot be safe to use it for throwing ligh
The Quarterly journal of the Geological Society of London . receding-septa. These facts run counter to, the views of Eiefstahl ^supported by Buckman ^; and, along with the observations ofWilley (1902) upon Xautihis, they furnish further support, ifsuch be needed, for those of Bather ^ and Appellof.^ According toRiefstahl, the last septum was formed in contact with the previousone, and became separated by the growth of the interveningshell-wall. He based his view upon the microscopical studyof tlie sepion. This, however, is so highly modified that it wouldnot be safe to use it for throwing light upon the formation of theseptum of the (comparatively) closely-allied l)elemnite, still lessupon that of the only very distantly-related ammonite. YII. The Deyelopmext of the Septum ofDactylioceeas commcxe. (1) The Second Sejitum. A wax model enlargement was made of the second septum, andfrom this a contoured plan (fig. 6) and a grajDh (fig. 7), like those Fig. 6.— Contoured ])^an of the second septum o/Dactyliocerascommune shoivn in PI. Ill, Jic/. [Explanation as in fig. 4 (p. 32). The contours are drawn at intervalsof OOl mm.] already described for the adult septum, were constructed. The ^ Die Sepienschale & ihre Beziehung zu den Belemniten Palfeontographica,vol. xxxii (1886) p. 20. - Notes on Nautili & Belemnites Proc. Geol. Soc. vol. xlvii (1891) p. 165. =* Shell-Gro^vth in Cephalopoda Ann. Mag. Nat. Hist. ser. 6, vol. i (1888)?p. 298. ?* Die Schalen von Sepia. Spinila, & Navtilus Kongl. Svenska Yetenskaps-Akad. Handl. vol. xxv, No. 7 (1893) p. 28. part 1] ox THE MOEtilOLOGr OF THE AMMONITE SEPTUM. 37 septum itself was 0*95 mm. broad, and 022 mm. from dorsmn toventer. The extreme antero-posterior range from the crest of thesaddles to the trough of the lobes was 016 mm. The area shadedin the ])lan is comparable with the flattened area of the adult, butis relatively much less extensive. It lies between contours 0*03 , and occupies 30 per cent, of the area of t
Size: 1929px × 1295px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1840, booksubjectgeology, bookyear1845
