8o 
Oliver . — On Physostoma elegans , Williamson , 
Text-fig. 3. Diagrammatic sketch of a median longitudinal section of Physostojna elegans , 
upon which are plotted the approximate positions of the planes of section of the principal sections 
figured in the present paper. The reference letters and numbers given with each section on the 
figure are the designations under which the preparations are cited in the explanation to the plates 
W. = Williamson Collection. M.H. = Prof. Bertrand’s Collection. S. = Scott Collection. R. 
and K. = University College, London, Collection. B. == Prof. Bottomley’s Collection. 
