154 SYSTEMATIC ARRANGEMENT 



ttl" Pillar-lip with a small notch in front, forming a slight tooth. 



16. ChLOROSTOMA. 



Shell top-shaped, smooth, solid ; axis umbilicated or perforated, 

 more or less completely covered with a callous deposit ; aperture 

 oblique ; pillar-lip arched, with a slight notch, forming a small tooth 

 in front ; outer lip angular behind. Operculum horny, many- 

 whorled. 



1. C. atrum, Adams, Gen. Moll. 428. t. 49. f. 1 a, operculum. 



Some specimens of the species of this genus are perforated, or 

 even umbilicated, when the type is imperforated. 



17. Omphalitis. 

 Shell top-shaped, granulated, solid ; axis perforated, open ; inner 

 edge of whorls sharply keeled ; aperture subquadrate ; pillar-lip 

 with a notch, forming one tooth and sometimes more teeth in front. 

 Operculum circular, flat, many-whorled. — Adams, Gen. Moll. 429. 

 t. 49. f. la. 



* Shell conical, granulated ; outer lip contracted. 



1. O. quadricostatus. 



2. O. Byronianus. 



3. O. aureotinctus. 



4. O. maculatostriatus. 



5. O. lividomaculatus. 



** Shell conical ; outer lip extended. 



6. O. excavatus. 



*** Shell depressed, smooth. 



7. O. roseus. 



**** Shell conical, elevated, tubercular. 



8. O. declivis. 



18. MONILIA. 



Shell depressed, subconic, thick, spirally striated ; axis perforated, 

 open ; inner edge of whorls with a striated callous band ; aperture 

 round ; pillar-lip arched, with a notch in front forming one or more 



small tubercles. Operculum of a few gradually enlarging whorls. 



Adams, Gen. Moll. t. 49. f. 3 a. 



1 . M. callifera. 



§§§§§ Axis umbilicated ; inner edge of whorls crenated. 

 19. Philippia. 

 Shell conical, umbilicated ; whorls compressed, subquadrate, with 



