X AGNATHOMORPHA. 



c 1 . Shell oblong, ovate-conic, subcylindric or 

 turrite, usually with the columella truncate 

 or sinuous at base. Kidney triangular, its 

 longest axis obliquely diverging from the 

 pericardium. Tropical American and Medit- 

 terranean. Oleacinida. 



ft 1 . Pulmonary vein apparently without lateral 

 branches, the lung without other noticeable (macro- 

 scopic) venation. Shell Planorboid, Helicoid or 

 Pupiform, usually with smooth, thin, transparent 

 cuticle (rarely yellow or dark) ; columella entire. 

 c. Jaw not distinctly developed. Kidney short, 

 oval, transverse, extending across the base of 

 the lung. Tropical. Streptaxida. 



c 1 . Jaw well developed, smooth. Kidney oblong, 

 longer than the pericardium and parallel to 

 it. America. Circinariida. 



Family STREPTAXID^E Gray. 



This family is African, Oriental and Tropical American. 

 Little is known of the soft anatomy, but in Streptaxis de- 

 formis (Fer.), which I have dissected, it appears that the 

 pallial organs differ widely from the Rhytididce. The lung 

 (pi. 52, fig. 5, 8. deformis, Barbados) is long and narrow, 

 with no visible venation except the pulmonary vein, a 

 fleshy ridge accompanying this near its anterior end. 

 The kidney is oval, transverse, extending across the base of 

 the lung, with a sigmoid ureter and closed, tubular secondary 

 or gut ureter. The cerebral ganglia are almost in contact, 

 the commissure very short. The following genera are re- 

 ferred here: Guestieria, Systrophia, Artemon, Streptaxis, 

 Priodiscus, Imperturbatia, Glyptoconus, Micrartemon, Gibbus, 

 Gibbulina, Ennea, Streptostele, Obeliscella. 



Family CIRCINARIIDJE Pilsbry. 



A wholly American group, closely related to the Strep- 

 taxidce by the discoidal Helicoid shell and the lung, yet dif- 

 fering by the normal form and position of the kidney, and the 



