658 BROWN AND o'CGNNELL THE JURASSIC OF CUBA 



of formation names, for not only does the usage vary from country to 

 country, but also within each country. It would be out of place in this 

 paper to discuss the reasons for adopting one set of terms rather than 

 another, in the European classification, but it may be stated that, in so 

 far as possible, we have employed the formation names of the type sec- 

 tions of England, whence all of the names were derived, and have used 

 the detailed paleontological zones now recognized on the Continent, where 

 the marine series is more completely developed than in Great Britain. 

 In England the Middle or Oxford Oolites include the Oxfordian below 

 and Corallian above, the former being again divided into the Callovian 

 or Kellaways rock, containing Kepplerites calloviense, a species found 

 in the zone of Macrocephalites macrocephalus on the .Continent, and the 

 Oxford clay with Cosmoceras jason, C. ornatum, Quenstedticeras lam- 

 berti, Peltoceras atlileta, and Cardioceras cordatum. These two divisions 

 in their faunal content correspond to the upper part of Quenstedt's 

 Brown Jura £. The Corallian, the upper part of the Oxford Oolites, 

 shows at the base the zone of Aspidoceras perarmatum and, higher up, 

 the zone of Perisphinctes plicatilis, the two being the equivalents of 

 Quenstedt's "White Jura a and /?, respectively, corresponding to Oppel's 

 zones of Transversarius and Bimammatus. 22, 



De Lapparent 24 uses Callovien in a somewhat broader sense than the 

 English do, making it include the Kellaways rock and the lower Oxford 

 clay, with Quenstedticeras lamberti and Cosmoceras jason as the zonal 

 fossils. His Oxfordien contains a lower division corresponding to the 

 English lower Calcareous grit, and an upper division which he calls the 

 Argovien and which is about the equivalent of the lower part of the 

 English Corallian. Coordinate with the Oxfordien is the next younger 

 division, the Sequanien, divided into the lower, or Eauracien, 25 with 

 Peltoceras bicristatum, and the upper, or Astartien, division, the Se- 

 quanien (sensu stricto), with Ostrea deltoidea. As De Lapparent uses 

 these substages, they bridge the paleontological zones and are there- 

 fore difficult to employ in correlation. Thus the Eauracien contains the 

 zone of Peltoceras bicristatum and a part of the zone of Perisphinctes 

 achilleSj while the Sequanien (sensu stricto) is considered to embrace 

 the beds in which P. achilles is dominant and also the lower Tenuilobatus 

 beds of the Swiss region. The Kimeridgien has been divided by Lappa- 



88 Ammonites bimammatus, which is the zonal fossil, is now designated Peltoceras 

 bicristatum (Kilian, Bull. Soc. Geol. France (4), ii, p. 783), but the name Bimammatus 

 zone is firmly fixed in the literature, having been employed for sixty years, and it is 

 still widely used instead of Bicristatum zone. 



24 A. de Lapparent : Traite de Geologie. Paris, ii, 1906, p. 1245. 



25 Proposed by Greppin, 1867. 



