GRAMMOCERAS TOARCENSE. 109 



Ammonites confined to the period we have mentioned. The strata with which it 

 deals are divided into the zones of Am. hifrons* and Am. opalinas ; and we may 

 take it that the former probably includes the Jurense-zone, together with a certain 

 portion of what is referred to in this Monograph as the Commune-zone. A large 

 proportion of the species figured by Dumortier are now found in our English 

 strata. 



Branco : " Der Untere Dogger Deutsch-Lothringens," ' Abhandlung zur geoio- 

 gischen Spez.-Karte von Elsass-Lothringen,' Band ii, Heft 1, Strasburg, 1879. 

 This work is remarkable for the extreme excellence of its plates. Under the 

 generic name Har-poceras, species of the genera Bmnortieria and Grammoceras are 

 included — in fact, in one or two instances specimens really belonging to the two 

 genera are referred to the same species. I have always been especially struck with 

 the extreme accuracy of delineation displayed in the plates of this work, because the 

 little-noticeable points which separate some species of Dumortieria from Grammo- 

 ceras are all brought out with the greatest accuracy, so that the task of separating 

 the members of the two genera is rendered comparatively easy. For studies and 

 drawings of the inner whorls of many species this work is also to be noted. 



A. Denckmann : " Fauna von Dornten," ' Abhandlung zur geologischen Special- 

 karte von Preussen und den thiiringischen Staaten,' Band viii, Heft 2, Berlin, 

 1887. This work contains many new species of Grammoceras, concerning which 

 the following pages will give further information. The species are worked out with 

 very considerable care, and many of them are evidently very closely related. Hence 

 to discriminate between the various species intended is a matter of extreme difii- 

 culty, which has been rendered all the harder by the fact that the author has, in 

 some cases, been unable to give us sufficient details, especially in regard to front and 

 back views. Where species are so very similar the want of these details presses 

 somewhat hardly on those who try to interpret the work. With a limited number 

 of specimens this interpretation would have been a matter of impossibility. 



Grammoceeas TOARCENSE (d'OrMgny). Plate XXVIII, figs. 4 — 13; Plate XXXIV, 



fig. 12; and intermediate form, Gramm. 

 toarcense-striatulum, Plate XXVIII, figs. 

 14, 15. 



1830. Ammonites eadiaws, Zieten (lou Reinecke). Versteiu. Wiirt., pi. iv, 



figs. 3 a, b, c. 

 1843. — Trov A.B,s-E^sis, d'Orliffnj/. Ceph. Jurass., Pal. Frau^., pi. Ivii, 



p. 222. 



' See p. 114. 



22 



