36 SYSTEMATIC ARRANGEMENT 



b. Volutomitrina. Siphon simple at the base. Tentacles close 

 together at the base. Mantle enclosed. Operculum none. 

 Teeth with a narrow angular diverging base and a single conical 

 apex. 



10. VOLUTOMITRA. 



1. V. Groenlandica, Adams, Gen. Moll. t. 19. f. 2, shell only. 



The foot of Volutomitra Groenlandica is obliquely folded across. 

 Mantle enclosed. Siphon simple at the base. Tentacles close at 

 the base, subulate, with eyes on large tubercles one-third above the 

 base. Operculum none. Male ; penis subcylindrical, folded back. 



c. Porcellanina. Siphon simple at the base. Tentacles close to- 

 gether at the base. Mantle lobes expanded, covering the shell. 

 Teeth in a single series, broad, transverse, band-like, with nine 

 denticulations in front . Operculum none. Shell covered with 

 a polished coat over the periostraca. 



11. PoRCELLANA. 



Shell ovate ; spire conic ; mouth oblong, longitudinal ; pillar 

 with five distinct plaits in front. Mantle covering part of the 

 shell. 



1. P. glabella, t. 102. f. 11, 12. 



2. P. quinqueplicata, t. 83 a. f. 4 ; Petit, Journ. Conch. 38. 



3. P. , n. s., t. 86 a. f. 4. 



4. P. ?marginella, t. 102. f. 8, shell naked? 



5. P. secalina, 1. 102. f. 4 ; Adams, Gen. Moll. t. 20. f. 5. 



6. P. ?, t. 102. f. 7. 



7. P. diadochus (Marginella d.), Adams, Gen. Moll. t. 20. f. 2. 



The mantle edge of Porcellana quinqueplicata is thin, enclosed 

 when contracted from being in spirits ; edge crumpled, free for half 

 an inch on the pillar side. Foot moderate, folded longitudinally, 

 double-edged in front. Siphon distinct, thick, without any auricle 

 at the base. Tentacles subulate, thin, the right smaller, close at 

 the base, united by a membranous band beneath, with the eyes on 

 the outer side of the base. Proboscis quite retractile, short, thick. 

 Lingual band elongate, transparent, convex, higher in the middle. 

 Teeth in a single series, transverse, three times as broad as long ; 

 the front edge straight, with nine small teeth, the central rather 

 the largest and further apart from each other, and the outer lateral 

 smaller, with the angle sometimes wanting. 



12. Closia. 



Shell ovate, polished ; spire very short ; mouth linear ; pillar 

 with four plaits in front ; plaits all close together, the two front 

 largest and equal, two hinder smaller ; outer lip crenulated. 

 1 . C. Sarda. 



