68 DR. L. F. SPATH ON THE AMMONITES [vol. Ixxix,. 



Quenstedt, or 0. F. Parana's l Agassiceras nodosaries (Quen- 

 stedt), of equally doubtful preservation. There is, then, no 

 trace of JEtomoceras in these beds. Similarly, there is no true 

 Agassiceras in the scipionianwm beds of Broadford in Skye. hut 

 only the more or less homceomorphous JEtomoceras development 

 mentioned below. 



Little importance, therefore, can be attached to individual 

 identifications ; but the association of forms is, in my opinion at 

 least, of the greatest significance. If it were not for the fact that 

 it might give rise to serious misidentifications, I would even prefer 

 J. F. Blake's 2 or E. Haug's 3 uniting of Ammonites [JEtomoceras] 

 personatas Simpson, with A. scipionianus, to Buckman's 4 rele- 

 gation of it to Agassiceras, which latter genus develops similar- 

 forms at a later date. Biological speculations in palaeontology, if 

 not based on careful collecting, are generally useless. In fact, it 

 appears from the present discoveries that in A. Hyatt's subseries, 

 for instance, containing A. hartmanni, 5 the ' degenerate ' form is. 

 the earlier, and the 'anagenetic' one is the later in origin, thus 

 showing that the development of ammonites is not always in 

 accordance with the current ' laws.' 



(B) Genus Arnioceras Hyatt. 



This genus is the one that is most abundantly represented in 

 the Shales-with-Beef. It ranges from beds beneath the lowest 

 horizon here dealt with up to the Black Arnioceras Limestone 

 ( = hartmanni-bed, 74 f), that is to say, there are some 53 feet of" 

 Arnioceras-benrmg strata in the ' Shales-with-Beef ' alone, not in- 

 cluding beds below (53) Table Ledge, where a number of earlier 

 series of Arnioceras are expected to occur. 



Now Arnioceras ceras (Griebel) Hauer sp., generally taken to be 

 a typical Arnioceras, is one of these early forms, and close to 

 A. geometricum (Oppel) and ^4. ceratitoicles (Quenstedt) Schmidt, 

 which species are associated in the Harzburg Ironstone 6 with 

 ' Goroniceras ' belonging to beds below the gmuendense subzone. 

 To judge by the results of my collecting in Skye, the 'Arnioceras ' 

 of the gmuendense and those of the scipionianum subzones are 

 different, both from the Arnioceras of the beds below and from 

 ' Epamioceras'' of the semicostatum type above. For A. Jcridion 



1 ' Contribuzione alia Conoscenza delle Ammoniti Liasiche di Lombardia,. 

 pt. iii: Ammoniti del Calcare Nero di Moltrasio, &c.' Mem. Soc. Pai. Suisse, 

 vol. xxv (1898) pi. xv, figs. 1 & 2. 



2 E. Tate & J. F. Blake, ' The Yorkshire Lias ' 1876, p. 287. 



3 'TJeber die Polymorphida?, eine neue Ammonitenfamilie aus dem Lias' 

 Neues Jahrb. vol. ii (1887), p. 97. 



4 ' Yorkshire Type- Ammonites ' vol. iii (1920) p. xxiv & pi. clxxxvii. 



5 ' Genesis of the Arietida? ' Smithson. Contrib. 673 (1889) Summary, 

 pi. xii [vol. xxvi, 1890]. 



R E. W. Schmidt, ' Die Arieten des Unteren Lias von Harzburg,' in J. F. 

 Pompeckj, ' Beitriige zur Palaontologie & Stratigraphie des Nbrdwest- 

 deutschen Jura ' Palaeontographica, vol. lxi (1914) p. 4. 



