PLATE IX 



Figure 21. Velutina laevigata. 



24. (B), Natica heros. 



(C), outline of adult shell reduced to size of early stage 

 showing difference of form. 



40. (C), Busycon canaliculatum. 



42. (A), Trichotropis borealis. 



46.^ Melampus bidentatus. 



(A), top view of nucleus. 



47. Diaphana debilis. 



(A), shows the reversed nucleus. 



48. Philine sp^ 



49. Vermetus lumbricalis. 



