part 1] jukassic chkoxology : lias. 87 



species being found in contact as a proof of their contemporaneity. 

 But experience of tliis and of many other cases has shown that the 

 finding of specimens in the same block of rock, however closely 

 they may be in contact, is no proof of contemporaneity; therefore 

 Geyer's insistance on this point makes no impression. Seeing is 

 not believing in such cases, and scepticism about contemporaneity 

 is always advisable : faunal analysis will soon detect the false 

 cases. 



The Wellow example is interesting, because of the great similarity 

 of the two matrices which coalesce — in other cases, some difference 

 of matrix may excite suspicion. But I think that the Wellow case 

 with its coalescence of like matrices goes a long way to explain the 

 Hierlatz fauna, allowing for the Hierlatz case possibly several non- 

 sequences and a good deal of redeposition. 



Looking at the Hierlatz ammonite fauna as figured by Geyer l 

 I judge the main of the comparable species to represent the 

 following dates : — 



Raasayan 3, bispinigerum, 

 Raasayan 1, 1st Echioceras, 

 Deiran 2, simpsoni, 

 Deiran 1, Gagaticeras, 

 Mercian 7 [b], subpolita, 



with certain derived species from lower horizons like Lymian 7 

 (Arnioceras). Thus, so far as Raasayan 1 and Mercian 7 [b] are 

 concerned, Hierlatz may be compared with the Gloucestershire 

 deposits described by Mr. Richardson. 



Much the same explanation may, I think, be applied to any 

 supposed admixture of species of different dates in the strata 

 of Spezia ; but, with one or two exceptions, the fauna of that area 

 is not comparable in date with those now under consideration from 

 Gloucestershire. 



(b) Concerning Small and Large Ammonites. 



The series of small ammonites yielded by the strata of Hierlatz 

 and Spezia suggest at first sight the idea that these localities show 

 dwarf Ammonite faunas of Liassic date at times when other 

 localities show faunas of large forms. This, I think, states a 

 general opinion, to which there would be a necessary corollary — 

 that the seas in which the small forms lived were more or less 

 separated from the seas of other areas, and were in some way 

 unfavourable to life. This would again involve a special delineation 

 of paheogeographical cartography, showing more or less landlocked 

 seas with restricted outlets. Now the work that has been done in 

 my former paper and to a certain extent in this one, suggests that 

 all this superstructure may rest on a very insecure foundation or 

 on no foundation at all. The small forms of Hierlatz and Spezia 

 would not be comparable with the large forms of other Liassic 

 areas, unless they were actually synchronous with them. In other 



1 VIII, pis. ii-iv. 



