146 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Certain Palaeozoic fossils, 

 which have hitherto been con- 

 founded with Orthoceras, but 

 which present no traces of 

 chambers, and in other re- 

 spects bear a close resem- 

 blance to the shells of Ptero- 

 poda, appear to belong to the 

 genus Creseis, though gigantic 

 in comparison with existing 

 forms. Both the species now 

 described and figured were ob- 

 tained from the Denbighshire 

 flag-stones. 



1. Creseis primceva. 



Very long, linear, dilated 

 towards the oral extremity, 

 smooth or with indistinct traces 

 of longitudinal grooves. 



Length of specimen (nearly entire) 



8 inches. 

 Breadth at the aperture \§ in. 

 Medium breadth ^ in. 



2. Creseis Sedgwicki. 



Shell cylindric, tapering, 

 linear, marked with very nu- 

 merous fine, regular, transverse 

 striae. Aperture dorsally an- 

 gular. 



Length of fragment || in. [Probable 

 length of specimen, 4^ inches. ] 



Breadth at aperture ^ in. 



Medium breadth ^ in. 



Breadth at the aperture of another 

 fragment T 8 5 in. 



1. Creseis primaeva E. Forbes. 



2. Creseis Sedgwicki E. Forbes. 



