SIXTH, OR OXYNOTICERAN BRANCH. 221 



are present also in Greenoughi, and therefore retain the separate appellation given 

 by him. There is also a possible relationship with the Oxyn. Oppeli of the Middle 

 Lias, which makes it desirable to keep it separate, for the present at least, from 

 Guibalianum. If it is a distinct species, or even a distinct variety, a? Greenoughi, it 

 may be the immediate ancestor of Oppeli. 



Oxynoticeras Oppeli, Schlon. 



Sum in. PI. XHI. Fig. 16. 



Oxynoticeras Oppeli, Schi.on., Zeifc. deutsch. Gesells., XV. p. 515. 



Amm. Oppeli, Schlon., Paleontogr., XIII. p. 161, pi. xxvi. fig. 4, 5. 



Amm. Oppeli, Dum., Etudes Pal. Bass, du Rhone, p. 125, pi. xxxv., xxxvi. 



Amm. oxynotus numismalis, Quenst., Amm. Schwab. Jura, p. 298, pi. xxxvii., fig. 4, 5 (not fig. 1-3, G, 7). 



The peculiar stout form of this species at the same age distinguishes it readily 

 from the Middle Lias congener of the same name described and figured by 

 Quenstedt. 1 The stout form of the young, gibbous sides, and the blunted abdo- 

 men, show that it may have been a member of a subseries in which Abattoense 

 was the first representative in the Lower Lias. The figure by Dumortier exhib- 

 its a prominent keel even at the diameter of 165 mm. Schlonbach's specimens 

 did not completely lose the keel until over 500 mm. in diameter. 



Geyer in his*Liass. Ceph. Hierlatz b. Hallstadt gives Oxyn. oxynotum, Guibali- 

 anum, and a form allied to the latter under the name of Oxyn. cf. Collenoti ; also 

 two undetermined species and a distorted form, named Oxyn. Janus. These are 

 all small and dwarfish, except the first, which, however, cannot be called large, 

 the largest individual measured by Geyer having been found to be only 74 mm. 

 in diameter. 



1 Amm. Schwab. Jura, pi. xxxvii. fig. 1-3, 6, 7. 



