AMPHIDOXA. 41 



row vertical grooves, which hardly crenulate the cutting edge. In 

 young examples it seems as if composed of narrow plates held 

 together by the underlying membrane (Schako). PL 1, fig. 15, A. 

 hookeri. 



Radula measuring 2'41 x '68 mill., consisting of 205 closely placed 

 transverse rows, each with 35, 51, 57 or 65 teeth. Formula 25-11- 

 1-11-25. Rhachidian tooth with a broad, blunt, rounded nieso- 

 cone, no side cusps. Laterals similar, the cusp often extending 

 beyond the thin basal-plate. Marginals tricuspid, the side cusps small 

 but distinct, obsolete on the outer marginals (pi. 1, fig. 14, A. 

 hookeri, showing teeth R, 1, 12, 17, 22, 25.) 



The principal peculiarity of the radii la is that the central and 

 lateral teeth possess mesocones only, in this respect differing from 

 the genera Endodonta and Phasis ; but as the dentition of but one 

 species is known, too much stress should not be laid upon this feature. 

 The close alliance of the toothless Endodontas (Charopa), the S. 

 African group Truchycystis, the northern genus Pyramidula, and the 

 S. American Amphidoxa-Stephanoda series, is evident. 



A. arctispira Pfr. iii, 47. A. lirata Couth, iii, 42. 



A. binneyana Pfr. iii, 48. A. magellanica Sm. iii, 42. 



A. bryophila Ph. iii, 42. A. musicola Ph. iii, 43. 



A. ceroides Pfr. iii, 47. A. ordinaria Sm. 



A. chilensis Miihlf. iii, 42. A. pazii Ph. iii, 43. 



A. coiquecana Ph. iii, 43. minviellet Ph. 



A. coppingeri Sm. iii, 42. A. pleurophora Moric. iii, 53. 



A. corticaria Ph. iii, 43. A. pusio King, iii, 47. 



A. costellata Orb. iii, 41. A. quadrata Fer. iii, 47. 



A. dissimilis Orb. iii, 48. kingi Pfr. 



histrio Miihlf. A. rigophila Mab. & Roch. viii, 

 playiata Beck. [81. 



A. epidermia Ant. iii, 42. A. selkirki Sm. iii, 47. 



A. exigua Ph. iii, 43. A. spirillus Old. 



A. germaini Ph. iii, 43. A. stelzneriaua Ph. iii. 43. 



A. gratioleti Hupe, iii, 48. A. strobeliana Ph. iii, 43. 



A. holmbergi Dor. iii, 43. A. tenuistriata Ph. iii, 48. 



A. hookeri Rve. iii, 48. A. tessellata Miihlf. iii, 47. 



A. hypophlcea Ph. iii, 43. contortula Fer. 



A. jungermanniarum Ph. iii, 43. A. zebrinaPh. iii, 48. 



A. leptotera Mab. & Roch. viii, 81. 



