166 VERMEIID^. 



faint median thread-like line ; color usually yellowish brown, the 

 early whorls chestnut. 



Operculum concave externally, with 5-6 spiral laminae, the 

 last abrupt; interiorly convex, shining, with irregular spiral 

 lirse; muscular area irregular, opaque. 



Subgenus BIVONIA, Gray, 1842. 



Shell affixed, mostly spiral, with spiral, interruptedly nodu- 

 lose lirse and a median elevated line; aperture contracted, 

 circular, columella without ridges. Operculum small, rudimen- 

 tary. . 



When these shells are not perfect, without the aperture 

 margin, they are difficult to distinguish from Spiroglyphus. 

 Dofania, Morch, 1860 (in part), is a synonym. 



Subgenus SPIROGLYPHUS, Daudin, 1800. 



Animal excavating a groove on the surface of shells or stones, 

 covering it over with shelly material, and thus forming a 

 tubular planorbiform case. Considered by some naturalists an 

 annulose animal allied to Serpula, but of this there is no proof. 

 When first hatched, the shell is spiral and regular, consisting of 

 one and a half whorls; it soon attaches itself, the channel it 

 excavates being at first shallow, afterwards deeper ; color bright 

 purple to nearly black. The operculum is large, thick, convex 

 exteriorly, with strong concentric laminre, plane interiorly, con- 

 centrically lirate, with central mamilla, and narrowly elevated 

 margin. 



Stoa, Serres, 1855, is in part a synonym. 



Subgenus THYLACODES, Guettard, 1774. 



Shell adherent, frequently solitary, tubular, irregularly twisted, 

 with 3-5 longitudinal nodulous lirge, aperture rounded, colu- 

 mella not plicate, but frequently partitioned internally perpen- 

 dicularly to the axis. No operculum, or minute when present. 



Dofania, Morch, 1860 (in part), is a synonym ; others are 

 Serpulorbis, Sassi, 1827 (a name frequently used for the genus), 

 Serpulus, Montf., 1810, and Serpuloides, Gray, 1850. The sub- 

 genera Cladopoda, Gray, 1840, Tetrancrnia, Morch, 1850, 



