TRANSACTIONS OF SECTION C. 561 



very numerous, the former being often iu the condition of imperfect phosphatic 

 casts. Above this band the round-backed ammonites entirely disappear, though 

 Belemnites lateralis continues to be fairly abundant up toD 1. 



It therefore appears that the southern Iloplites obtained full possession of the 

 area earlier than their associated southern belemnites of the jaculuin type, 

 although rare examples of these belemnites occur in the clays below D 2. 



The lower part of the zone of Belemnites jaculam, besides yielding many 

 Iloplites, contains occasional ammonites pertaining to the genera Holcodiscus 

 and Astieria (of the Olcostephani), and also to other genera. The higher beds are 

 occupied by Olcostephayd of the genus Simhirslates, but these beds have of late 

 years been so poorly exposed that no further information can be given regarding 

 the distribution of these forms. 



In the zone of Belemnites brunsmce7isis ammonites only occur at the extreme 

 base, where there are a few examples of one of the Simbirskites, and in its uppermost 

 beds, where the genus Hoplites, represented by H. Deshayesi, reappears associated 

 with forms of the genus Oppelia, the whole of the intervening deposits being appa- 

 rently devoid of these fossils. 



In the beds with Belemnites Ewaldi, which may prove to be a distinct zone 

 between the brunsvicensis and minimus zones, no ammonites have as yet been 

 detected, but in the miiiimus zone H. intemtptus, Brug., has been found. 



The Criocerata have been found to exist in most, if not all, the deposits from 

 the uppermost part of the Belemnites lateralis zone to the top of the Belemnites 

 brunsvicensis zone, and are especially numerous about the middle of the Belemnites 

 jaculum zone. They are, however, difficult to determine, being both fragmentary 

 and ill-preserved. 



The paper concluded with a list of the species of C'rioceras, including those 

 described in ' Argiles de Speeton ' and those met with by the author, and deter- 

 mined chiefly by Dr. A. von Koenen. This short list might, doubtless, be gi-eally 

 extended by anyone conversant with the forms of this group. 



FlilDAY, AUGUST 3. 

 The following Papers and Eeports were read : — 



1. The Post-Cretaceous Stratigraphy of Southern Nigeria, W.C.A. 

 By Jows Parkinson, B.A., Principal of the Mineral Survey. 



This preliminary account of the post-Oretaceous stratigraphy of Southern 

 Nigeria is the result of work carried out by the Mineral Survey between the 

 winter of 1903 and the summer of 1906. 



In adopting the following stratigraphical succession the author wishes it to be 

 understood that the country is densely forested and only partially mapped. In 

 descending order the beds are as follows : — 



1. Alluvium of rivers and lower terraces. 



2. Benin Sands. 



3. Ijebu Beds. 



4. Lignite Series. 



Four separate areas are described : — 



a. The Central Province (in part). 



b. The Asaba district on the N iger. 



c. The Ijebu district of the Western Province (Lagos Province). 



d. The Calabar district. 



The author concludes that stratigraphically the Benin Sands are the most im- 

 portant member of the series ; that their deposition marks a very pronounced 

 movement of subsidence, involving nearly all the soutbem half of the colony ; and 



1906. 



