174 L. F. Spath — Notes on Ammonites. 



Trachyostraca. In his later work, 1 however, he assumed, con- 

 formably to the general opinion, that the whole of the Jurassic and 

 Cretaceous Ammonites issued, by branching, from the family of the 

 Phylloceratidae, i.e. Liostraca. Steinmann, 2 on the other hand, still 

 maintains a purely artificial classification into Trachyostraca, 

 Hemiostraca, Liostraca, and Heterostraca. J. Boehm 3 also emphasizes 

 that from the study of Kossmaticeras it was clear that the systematic 

 division of Cephalopoda according to the mode of ornamentation was 

 an artificial one, and that stress was to be laid above all on the 

 ontogenetic development. 



But though unsuitable for general purposes, the ornamentation or 

 carination may be of considerable value for the minor groupings of 

 Ammonoids. The course of the radial line in certain Hildoceratids,* 

 the different types of costation in the Perisphinctids, an important 

 classificatory character, and in the ribbed descendants of Psiloceras, 

 the tendency to differentiate costation either on the venter (with 

 first thickened and then interrupted ribs) or on the side (with 

 eventual carination of the ventral area) separate the two important 

 families of Schlotheiminse and Arietidae. In the former, the 

 development that leads up to a grooved periphery (in the ontogeny 

 of the later forms) is separated generically( as Waehneroceras) from the 

 forms of the succeeding hemeras that have a similar tendency to lead 

 back from a grooved periphery to a rounded venter {Schlotheimia). 

 The terms anagenesis and catagenesis are avoided by the writer not 

 only because, for example, a smooth (so-called catagenetic) form may 

 show elaboration of all its other characters, but also because he 

 considers the smooth oxycones in many stocks to be specialized 



1 "Die Ceph. d. Hallstatter Kalke " : Abh. k.k. Eeichsanst., vol. vi, 

 1873-93, 2 vols. 



2 Einfiihrung in die Palaeontologie, 2nd ed., 1907. 



3 N. Jahrb. f. Miner., etc., ii, p. 463, 1912 (in review of Kalian & Eeboul's 

 paper on certain neo- Cretaceous Ammonites). 



4 The writer used this character in the subdivision of the Middle Liassic 

 (Domerian) Hildoceratids ("On Jurassic Ammonites from Jebel Zaghuan ": 

 Q.J.G.S., vol. lxix, pp. 547-52, 1913) and separated the Flexiradiata from the 

 rectiradiate forms that constitute the genus Scguenziceras . The genus Proto- 

 grammoceras was created for the former, and two divisions were recognized 

 within that genus ; but one of these, characterized by dionase in peripheral 

 projection and' including subanguliradiate and angulirursiradiate forms, is 

 covered by the genus Fuciniceras created just prior to the publication of the 

 writer's paper. The genus Protogrammoceras will, therefore, have to be 

 restricted to the forms of the first subdivision, including subfalciradiate and 

 falciradiate forms (type " Grammoceras" bassanii, Fucini, " Apenn. Cenfr.," 

 pi. x, fig. 6, 1900). Apart from their Domerian age, both the Eursiradiata 

 {Fuciniceras) and the Falciradiata {Protogrammoceras) are distinguished from ' 

 the Toarcian Harpocerates by their combination of evolute whorls with 

 a tendency to change the periphery from fastigate to carinatisulcate and back 

 again to fastigate. The form described and figured in that paper as gen. nov. 

 sp. nov. (?) (pi. lii, fig. 2, p. 556) belongs to the group of forms wrongly 

 referred to Harpoceratoides by Haas, and the new genus Lioceratoides (type 



' ' Lioceras (?) " Orecoi, Fucini, "Apenn. Centr.," Pal. Ital., vol. vi, p. 65, 

 pi. xi, fig. 4, 1900) is now proposed for this development, characterized by 

 a type of costation very distinct from that of the other Domerian Hildoceratids. 



