182 Annals of the Carnf.gie Museum. 



It is seen that B. hatcheri has, relatively to the width of the bridge, 

 large anterior and posterior lobes; that B. marshi has both lobes 

 small ; and that j9. callosa has the anterior lobe short and of moderate 

 width, while the hinder lobe is broad at the base. 



The description of B. marshi will soon appear in the American 

 Journal of Science. 



The anterior lobe of the plastron of the present species is narrower 

 and more pointed than that described by Lambe (Cont. Canad. 

 Palaeont., iii, 1902, p. 44, fig. 9) under the name Ba'ina antiqua. 



AMER1C.A.N Museum Natural Hisiory, 

 May, 1904. 



