Vol. 63.'] CRETACEOUS FOSSILS FROM BAHIA. 137 



postclavicular expansion of its middle part. The bone is marked 

 only by the ordinary lines of the structural fibres. 



Mr. Mawson has also obtained from the beach between Plataforma 

 and Itacaranha one fragment of a small Coelacanth fin-ray, exhibit- 

 ing the characteristic denticles arranged in an irregular double 

 series on the anterior face. 



Besides the typical remains of Maivsonia gigas, there are others 

 of the same genus which are doubtfully referable to this species. 

 One imperfect right parietal bone (B. M., No. P 86;, for example, is 

 much shorter in proportion to its width than the original of 

 PI. VII, fig. 4, while its external ornament is much coarser ; and 

 this specimen is interesting as being still articulated with the 

 postero-lateral plate of bone, which is usually interpreted as 

 squamosal -f- post- temporal. Part of a relatively-small ornamented 

 bone is suturally united with the inner border of the latter element, 

 aDd with the hinder border of the parietal. There is also a nearly- 

 complete left angular bone, not more than 27 centimetres in length, 

 resembling the corresponding element of the typical Mawsonia gigas 

 in shape, but with a coarser ornament forming large reticulations 

 on the lower part of the coronoid elevation. Finally, there is a still 

 smaller right angular from the Mapelle Quarry, in which external 

 ornament is almost lacking. With the latter must be associated 

 the hinder portion of an equally-small left dentary from the same 

 quarry, showing the raised portion which would abut against the 

 splenial. 



Mawsonia gigas is of especial interest as showing that, although 

 the Coelacanth fishes were, as a rule, of comparatively-small size 

 (the largest measuring considerably less than a metre in length), one 

 at least attained gigantic proportions just before the final extinction 

 of the family. 



Conclusion. 



If the vertebrate fauna now enumerated be compared with 

 European standards, it will be noticed that two of the four 

 commonest species are essentially Wealden in character, while the 

 two others are chiefly Middle or Upper Cretaceous forms. The 

 Goniopholid crocodiles are confined to the Wealden and Purbeck 

 horizons in Europe, while Lepidotus Maivsoni (although known only 

 by fragments) is evidently one of the latest species of the genus 

 closely similar to the well-known Wealden L. Mantelli. Chiro- 

 mystus Maivsoni, on the other hand, must be regarded as one of the 

 Chirocentridse or Ichthyodectidae which range upwards from the 

 Neocomian ; while Diplomystus longicostatus belongs to a genus 

 which is common in the Upper Cretaceous of the Lebanon, and is 

 abundant later in the freshwater Lower Tertiaries both in Europe 

 and in North America. Of the other species, Megalurus Maivsoni is 

 a Jurassic, rather than a Cretaceous type of Amioid fish; and 

 Maivsonia gigas may be either Jurassic or Cretaceous, although 

 theoretical considerations suggest that it should be referred to the 



Q. J. G. S. No. 250. l 



