The Invertebrate Fauna of the Uitenhage Scries. 227 



referred to a single genus, I have employed the name Gram- 

 matodon. The selection of a correct name for these and similar 

 Mesozoic forms might possibly be regarded as still debatable, 

 but in this matter I have deferred to the opinion of Mr. H. Woods 

 a view with which Dr. Wheelton Hind is now also in agreement. 

 In the choice between the generic names Gari and Psammobia 

 opinions are divided, but I have given reasons for preferring to 

 retain Psammobia (for Ps. atherstoni), although this course cannot 

 perhaps be strictly justified, except as a measure of expediency 

 to meet the circumstances of this particular instance. In the 

 case of Avicula baini, the generic name Pteria, which has the prior 

 claim, is used in one of the above lists. Gryphcea imbricata we 

 have seen to be more correctly referable to Exogyra, to which 

 it was originally assigned by Krauss, and I have pointed out that 

 there is no foundation whatever for the inclusion of the name 

 Trigonia goldfussi in any list of molluscs from the Uitenhage 

 Series. 



It should be remarked that the errors to which some of the 

 discrepancies above noted are due, are such as must almost inevi- 

 tably occur in a list of fossils which is compiled from previous 

 works, with attempt at revision, without the examination of actual 

 specimens, even though the task of compilation be carried out as 

 carefully as in Mr. Newton's paper. 



VI. SUMMARY.* 



General Results. The great majority of the invertebrate fossils 

 collected from the Uitenhage Beds consist of marine Mollusca, and 

 have been obtained from localities in the valleys of the Sunday's, 

 Zwartkop's, and Coega Eivers. The present study has shown that 

 these marine fossils in reality furnish evidence which enables us to 

 estimate their geological age with considerable precision. A more 

 detailed examination of the fauna than that undertaken by Neumayr 

 fully corroborates that author's conclusion that a large number of 

 the Mollusca show affinity to Cretaceous rather than to Jurassic 

 forms. The broad question of age which has given rise to such widely 

 different expressions of opinion is, in fact, decisively answered 

 by the occurrence of representatives of the following genera : 

 Holcostephanus (sensu stricto) ; Hamites ; Crioceras ; Bochianites ; 

 Acanthodiscus; Trigonia (divisions Scabrae and Pseudo-quadratae) ; 



* See also Kitchin (2). 



