176 A'ERMETUS. 



Subgenus BIVONTA, Gray, 1842. 

 V. TRIQUETRA, Bivona. PI. 50, figs. 41, 42. 



Solitary or gregarious, subtriangular, a little depressed, orbicu- 

 larly or turbiuately twisted, transversely flexuosely rugose, 

 anterior portion of the shell when free, becoming C3 r lindrical, 

 but if remaining attached, continuing subtriangular; whitish or 

 brownish. 



Mediterranean Sea. 

 V. contortuplicatuti, Var., A. Scacchi, is a synonym. 



Var. PINNICOLA, Morch. Irregularly spiral, with three crenulated 

 longitudinal lines. It is V. granulatus, Graven., not Fabr., 

 and perhaps V. rupestris, Risso. 



Tar. SPIRORBIS, Morch. Solitary, white, cretaceous, spirorbiform , 

 with a crenulated dorsal carina, and one or two arcuate 

 varices in the penultimate whorl. 



Yar. ALETES, Morch. Laterally affixed, whorls flattened, ob- 

 liquely declined ; dorsal carina compressed, crenulated, 

 approximating the umbilicus ; incremental striae membran- 

 aceous, obsoletely undulated in the umbilical region. 



Vars. SERPULINA, EXPANSA and AMPLIATA, Morch. 



Var. FASCICULARIS, Morch (fig. 42). Shells aggregating, base 

 spiral, anteriorly upright, rounded. Forms a transition to 

 the next species, from which perhaps it does not differ. 



V. SEMISURRECTUS, Bivona. PL 51, fig. 44. 



Solitary, cylindrical, white, apex contorted, rugose, adnate, 

 anteriorly the tube is free, flexuose, longitudinally striate or 

 almost smooth. Mediterranean Sea. 



V. SEQUENSIANUS, Avadas and Benoit. PL 51, fig. 45. 



Irregularly spirally twisted and attached below, finally becom- 

 ing erect; whorls at first angulated, rugosely longitudinally 

 striate, and with stong incremental striae, the free portion be- 

 coming cylindrical and smooth, rather fragile, gregarious. 



Sicily. 

 V. QUOYI, H. and A. Adams. PL 51, fig. 46. 



Solitary, loosely contorted, rather thin, livid white, brown 

 clouded, attached at the end, last whorl long, flexuous, with 



