230 HELICOSTYLA. 



H. quadras! Hid., viii, 34. H. stramihea Semp., viii, 39. 



eossmanniana Cr. H. cumingi Pfr., viii, 39. 



H. modesta Sowb., viii, 35. H. segle Brod., viii, 40. 



B. hindsi Pfr. v. barandse Hid., viii, 40. 



B. verecundus Rve. H. oviformis Semp., viii, 40. 



H. belcheri Pfr., viii, 35. H. uber Pfr., viii, 41. 



B, hindsi Rve. H. phseostyla Pfr., viii, 41. 

 H. lacerata Semp., viii, 36. 



paradoxa Semp., olim. 



Section Phengus Albers, 1850. 



Phengus ALB., Die Hel., p. 137, for B. opa linns and B. evanes- 

 cens. v. MART., Die Hel., 1860, p. 180, type H. opalina. 



Shell thin, pale green, distinctly trochoidal, and with no hydroph- 

 anous cuticle. Type H. opalina Sowb., pi. 53, fig. 5. 



These shells have the texture and color of Eudoxus, but differ in 

 their trochiform contour. Anatomically, Phengus forms a transi- 

 tion to Canistrum, the dart sack being small and without a dart, 

 and the globular mucus gland is much reduced in size. 



H. opalina Sowb., viii, 42. H. dumonti Pfr., viii, 42. 



Section Canistrum Morch, 1852. 



Canistrum MORCH, Catal. Yoldi, p. 31. PILS., Manual viii, p. 

 43. 



Shell ovate-conic or oblong, imperforate and solid ; banded ; with 

 or without hydrophanous cuticle ; surface microscopically spirally 

 striated ; whorls narrow ; lip well expanded ; columella vertical. 

 Type H. ovoidea Brug., pi. 53, fig. 4. 



Genital system as in Helicostyla except that the dart sack and 

 mucus glands are absent (pi. 54, fig. 1, H. stabilis). 



That the simplicity of the generative system is probably the re- 

 sult of degeneration of the dart apparatus is shown by the approach 

 to this condition in Phengus. The anatomy of Canistrum is other- 

 wise as in Helicostyla. It is very desirable that more species be 

 examined anatomically, for intermediate stages of development. 

 When Prochilus and Chrysallis are dissected, their anatomy may 

 throw light upon the condition of Canistrum. 



H. ovoidea Brug., viii, 43. costerii Eyd. 



luzonicus Sowb. euryzonus Pfr. 



