Ill ill. OK v. IS.SU Kl: \N BRANCH 199 



maintains the aspect ol until a late period of growth, and then 



develops the keel and form <>i' Seipioiiiaiiiin . and tin • another fossil, which 



1 1 \ similar tt> tin- later, but >t ill immature, ai 

 The k<-el may, perhaps, have a hollow above the riphon, such as Quenstedt 

 i hia u Lmmoniten «K-.^ Schwabischen Jura," Plate XIV, Fig. 1, but 

 tin.- inner or nacreous layer does n<>t form a partition between tin- interior of the 

 shell and the interior of the keel, nor does the black la above ilu~ par- 



tition, m and others, which have true hollow keels. In the 



specimens examined, the keel was elevated, as in Quenstedt's figure, but the 

 aiphon laid directly against the Bhell layers, which 1 ■ 1 1 e-« 1 the interior of ih. 

 and there was no black layer. 



Agassiceras nodosarios, Hyatt. 



Amr< .lur.i. p 7- pi vui li,-. S; Alum Sehwib J 



y — Bempflii 



The specimen of tlii< Bpecies in the Museum of Comparative Zodlo 

 compressed than those figured I»\ Quenstedt, but it Bhows that n ■ prob- 



ably quite distinct from >S The whorls are more compressed than iu 



the latter, l>ut the tubercles and pilaa are retained until a much later age. These 

 .-.in !•• distinctions are, of course, -till more marked when the species is compared 

 with s I ict horizon was not marked on om- specimen. The 



red 160 mm., and the outer whorl 60 mm., the same whorl at the 

 tewhat less than 30 mm. ; the greatest transverse diameter 

 of 1 1 1 • - same w ■ 10 mm., and the least about 20 mm. Our specimen i>. 



therefore, a trifle larger than the inner whorl of the fragment figured l»\ Quen- 

 stedt in " Ammoniten des Schwiibischen Jura," Plate W II Fig I, at the point 

 mark same diameter a~ hi* abdominal \ i 



mme whorl marked "q." The keel is also in the same condition, being 



: with matn\. the geniculsB are bent and run nearly to the keel, there are 



i on the younger part of tlii< whorl the keel is well preserved and 



mens were found in the Tuberculatus * • « - » 1 - It i* 



not unlikely that the compressed varietj "i I s ibove 



ought to be transferred t<> tl but we li:i \ < - not been able to gather 



ttle tlii- question 



Agassiceru* Sripionis, Hi 



PMl li .11X1111 



Amr. 



- 



The shell <>f I 



in form and 



t^lleii 



