x BULIMULID^E. 



II. OooNTOSTOMiNvE. Shell varying from fusiform to Helicoid. 

 Aperture usually obstructed by internal lamellae, folds or 

 teeth. Jaw plaited or solid. Dentition Helicid. Genitalia 

 simple. 



III. ORTHALICIN^E. Shell ovate-conic or oblong, imperforate, with 



solid axis, usually rather large and strikingly colored, the 

 aperture toothless, sometimes with a columellar fold. Jaw 

 strong, with rather few, wide plaits. Teeth in V shaped 

 rows, bearing single broad, gouge-shaped cusps, the median 

 teeth sometimes lance-shaped. Penis provided with an 

 accessory gland or appendix. 



IV. AMPHIBULIMIN^E. Shell more or less degenerate, globose, 



oblong, /SMccmm-shaped or Haliotis- shaped, always thin and 



mainly cuticular. Jaw very delicate and highly arched, 



composed of many close, converging plaits. Radula variously 



specialized, the cusps large. Genitalia simple. 



With the exception of the last subfamily, these groups seem to be 



natural. The main lines of generic affinity, and approximate phy- 



logeny, may then be represented by the accompanying diagram. The 



relationships of the genera of Orthalicince to one another have been 



considered elsewhere (vol. xii, p. 100), those of the genera of Odon- 



tostominse in this volume. 



ODONTOSTOMIN. 



ORTHALICINCE. 



