PLEUROTOMID^E. 161 



Section PLEUROTOMELLA, Yerrill, 1873. Shell somewhat tur- 

 reted ; apical whorls smooth ; the others shouldered and ribbed, 

 but with a smootji concave surface above the shoulder ; lip-sinus . 

 wide, very deep ; canal short. Animal blind. 



Section MITROMORPHA, A. Adams, 1865. Shell small, Mitri- 

 form, with revolving lirse, and sometimes longitudinally plicate; 

 columella straight, bearing a number of short plicae or teeth 

 upon it ; lip acute, smooth within, scarcely sinuated posteriorly. 

 California, Japan. 



This group has sometimes been referred to Mitra (see Manual, 

 iv, 145), but the armament of the columella is not always present, 

 and when it is, it more resembles a set of small callous deposits 

 than revolving plicae. 



Subgenus APHANITOMA, Bellardi, 1815. 



Shell fusiform ; sinus scarcely apparent ; columella nearly 

 straight, biplicate ; canal rather short, slightly curved. Tertiary 

 only. Europe. 



Genus HALIA, Risso, 1826. 



Shell oval-oblong, ventricose, thin, fragile, shining, smooth; 

 spire obtuse ; aperture oval ; columella truncated at the base ; lip 

 simple, arcuated, slightly sinuous. 



One living species, Atlantic near Cadiz, and N. W. Africa; 

 fossil, a species in the pliocene of N. Italy. 



The classification of this mollusk has a long and interesting 

 history, which is given with some detail in a paper by Dr. Paul 

 Fischer, entitled " Monographic du genre Halia Risso (Priamus 

 Beck)," published in Journal de Conchyl., 2d ser., iii, 141. 

 There was great uncertainty until within comparatively recent 

 times, as to its habitat whether terrestrial or marine, and the 

 animal remained unknown until 1858. Various ancient authors 

 classed it successively as a Helix, Buccinum, Bulla, Bulimus, 

 Achatina (Lamarck), Cochlicopa (Pfeiffer : Helicidaa). 



In 1838, Deshayes published the genus Priamus, Beck, and 

 made it an operculated marine shell between Buccinum and 

 Struthiolaria ; and since that period and up to 1858 the shell 

 has been generally classed in the neighborhood of the Strombs 

 or Buccinidse. 



Hermannsen, in 1846, discovered that Priamus was identical 



