xlii. COI^CHYUA—DITHYMA. 



4. subrufus, radiis suhviginti Itevihts. 



with about 20 smooth rays. 



5. sinuosus, vari^ distortus, slriis numerosis echinalis. 



variously distorted, with numerous prickly rays, 



6. glaber, striis transversis minutissimis. 



with very minute transverse striae. 



7. turaidus, glaberrimus, latere altero producto, 



quite smooth, produced at one of the sides. 



** auriculis incBqualibus. 

 with the auricles unequal. 



8. laevis, planatus, pellucidus, glaberrimus. 



flattish, transparent, and quite smooth. 



9. obsoletus, striis minutissimis longitudinalibiis subiuulalis. 



with very minute longitudinal undulate striae. 



10. varius, radiis 28 echinalis. 



with about 28 prickly rays. 



1 1 . Pusio, radiis 40, alternis minoribus. 



with about 40 rays which are alternately smaller. 



12. Islandicus, radiis numerosis bijidis. 



with numerous doubled rays. 



47. Lima. 



1. buUata, couvexa, striis subundatis intermediis minoribus. 



convex, with somewhat undulate striae and 

 smaller ones between them. 



