8. 8. Buckman — Jurassic Ammonites. 299 



Erycites especially, belong to the Mediterranean regions ; while the 

 Lytoceratites ^ were particularly abundant — in fact, individually and 

 specifically they would seem to have flourished, in the Mediterranean 

 districts as compared with this country, as ten to one. 



Two new genera are introduced in the present pamphlet, namely, 

 Paroniceras (Prof. Parona) and Collina (derivation not given, but 

 j)erbaps from CoUinus, "of a hill"). The type of Paroniceras is 

 J.m. sternalis (von Buch) ; and concerning its value in our opinion 

 see the appended paper on "The genus Cymhites." The type of 

 Collina is a new species, " gemma,'''' which may be described as 

 a carinate Dactylioceras allied to mucronatnm (d'Orbigny). The 

 carination appears to be the feature which separates Collina from 

 Dactylioceras ; and if it can be shown that Dactylioceras split up 

 into two branches, one of which developed a carina, and the other 

 remained uncarinate, the genus Collina (? CoUinus) will have good 

 foundation. 



Among specific names to be noted are, first, the application of 

 Oppel's " iserensis" to Am. erbaensis (Dumortier, non Hauer), a 

 very necessary correction ; and, second, the new name " Coeloceras ? 

 Mariotti " applied to Am. Hmnphriesianus nodosus (Quenstedt, Jura, 

 pi. 54:, fig. 4). This name, however, is superfluous, and must 

 rank as a synonym ; because Hyatt has already applied the name 

 "nodosum" to this very figure : he called it " Steplianoceras nodosum." ^ 

 It may be remarked that, in translating Quenstedt's trinomial or 

 quadrinomial system into modern currency, the first two names, 

 say "Ammonites Uumphriesianus," are really generic, and are con- 

 cisely written " Steplianoceras " or " Coeloceras," while the third name 

 thus becomes specific ; and, unless the restricted genus already 

 contain the same name, Quenstedt's third name should always be 

 used. Further, both Coeloceras and Dactylioceras have priority of 

 Steplianoceras, while a name Stephanoceros was already in use for 

 a genus of Kotatoria.^ 



Prof. Bonarelli places as Toarcian the Falciferum- to Jurense-zones, 

 and as Aalenian the Opalinum- to Concavum-zones. He discusses the 

 division between "Lias" and "Jura," and his conclusion is thus 

 expressed (p. 254) : " In the Central Apennines the most natural 

 division between Lias and Jura which it is possible to adopt is 

 precisely that proposed by Miinster and upheld by Vacek." That 



^ I propose this name as a sort of colloquial word, congruous with Ammonites, 

 Ceratites, Goniatites, etc., to distinguish those genera which are certainly not true 

 Ammonites, either in characters or by descent, namely, Lytoceras, Pleuracanthites, 

 Phylloceras, IlonophylUtes, etc. They are characterized by the phylliform cells of 

 the septa, and probably by the absence of any calcareous Aptychus or Anaptychus. 

 Lytoceratites are biologically lower than Ammonites, though they are collateral and 

 coeval. They were separated hy Hyatt (Genesis Arietidte, p. 4) as Lytoceratinm ; 

 but this places Lytoceratina superior to Lytoceratidce, whereas it should be of 

 inferior rank. The terms Lytoceratacece and Ammonacece (the latter used many 

 years ago) might indicate Lytoceratites and Ammonites respectively, and be sub- 

 divisions of Ammonoidea. 



* " Genetic Relations of Steplianoceras,'''' Proc. Boston Nat. Hist. Soc. vol. 18, 

 p. 386, 1876. 



^ Hyatt, op. cit. p. 368 (E. B. Tawney's information). 



