232 Reports & Proceedings — Geological Society of London. 



Hock described by Leckenby, preserved in tbe Sedgwick Museum, 

 Cambridge, and a series of Yorkshire Kelloway Hock ammonites 

 from the Museum of Practical Geology, London. He has grouped 

 these ammonites according to tlieir different matrices, and finds that 

 they indicate several different zones. These zones he arranges in 

 sequence, and suggests how they may be comjiared with tlie sections 

 of Kelloway Hock of Scarborough given by Leckenby and by Fox- 

 Strangways. The exact order of the zones is, in one or two cases, 

 not considered to be proved, but the paper is offered with the idea of 

 indicating where further work is required. 



An examination of the ammonite fauna of the Yorkshire zones 

 shows that the so-called ' Kelloway Eock ' of Yorkshire is in part 

 contemporaneous with the Oxford Clay of the Midlands and the 

 South of England, and in part contains faunal facies not represented 

 in these areas, but peculiar to Yorkshire so far as England is 

 concerned ; they show, however, some affinity with faunal facies in 

 Russia and in Normandy. 



An examination of the list of species of ammonites recorded by 

 Fox-Strangways from the Oxford Clay of Yorkshire shows ;hat the 

 Oxford Clay of Yorkshire itself is not in the main sequential to 

 the Kelloway Eock, but is contemporaneous with it, leading to the 

 inference that even in Yorlcshire itself part of the Kelloway Eock 

 is only a local manifestation, and that it passes laterally into 

 Oxford Clay. 



A table of zones is given, in order to illustrate the contemporaneity 

 of the Kelloway Eock - Oxford Clay deposits of Yorkshire and tlie 

 ]\tidlands, while at the same time showing the various non-sequences 

 in both areas. 



Some critical palaeontological remarks are made concerning the 

 identification of certain species of ammonites, and a correction of 

 nomenclature is made, with a new name for a species misidentified 

 on account of homoeomorphy. This leads to a few remarks on 

 development and homoeomorphy, wherein an important difference in 

 the mode of development of certain Kelloway Eock - Oxfoid Clay 

 genera is pointed out, and it is remarked that there are three methods 

 of homoeomorphy^ — (1) subparallel, the likeness of stocks passing 

 through similar stages; (2) transversal, the likeness of stoclis starting 

 from different forms meeting at a cross-over or collision-point ; and 

 (3) cyclical, the likeness of an anagenetic to a catagenetic series. 



2. "On Jurassic Ammonites from Jebel Zaghuan (Tunis)." By 

 Leonard Frank Spath, B.Sc, F.G.S. 



Jebel Zaghuan, the best-known and most conspicuous, though not 

 the highest, mountain of the Timisian Atlas, is built up largely of 

 massive bluish-grey limestones of confused stratification which have 

 been referred to tlie Middle Lias on the evidence of badly preserved 

 Belemnites and J'erehratuloi, notably ' Pygope ' aspasia, Columna sp. 

 Middle Liassic (Domerian) ammonites are now recorded for the 

 first time. A new classification of the Domerian genera of the family 

 Hildoceratidaj, to which the fossils from Jebel Zagiiuan belong, is 

 proposed. 



