270 "POLORTHUS. 



P. BILOBATUM, Desl. PI. 104, figs. 580, 581. Upper Lias of 

 Normandy. 



Genus POLORTHUS, llabb. 



The aggregated mass of specimens forming the type of this 

 genus was originally referred to Teredo ; subsequently, in des- 

 cribing the genus, Mr. Gabb referred it to Yermetidne, and in 

 1872 he finally believed it to be a cephalopod connecting the 

 Orthoceratidse with Beatrices. The aggregate character, the 

 long, narrow, irregular tube, the non-molluscan character of 

 the partitions forbid this determination : I am convinced that 

 Polorthus is not a mollusk, and Beatricea itself is now referred 

 doubtfully to the Spongiadse. 



