VERMETID^B. 167 



Hatina, Gray, 1847, and Lementina, Risso, 1826, are founded on 

 differences of form in the mollusk, mostly as represented by 

 published figures, and allowing that these are correct, their 

 value is probably no more than specific. These characters will 

 be referred to in the descriptions of the species. 



Subgenus SIPHONIUM (Brown, 1756), Morch, 1859. 



Shell adherent, irregularly twisted, carinated, without internal 

 armature. Operculum large, smooth, circular, concave exter- 

 nally, convex interiorly, the scar of attachment central, with 

 rugose concentric striae, and plain margin. 



M. Rougemont has observed at Naples that S. maximum 

 emits from its mouth a thin veil-like plaited substance, which 

 entangles small natatory animals and is subsequently with- 

 drawn (Bull. Soc. Neuch., xii, 94). 



Stoa, Serres, 1855 (in part), is a synonym, according to the 



text. 



Subgenus STEPHOPOMA, Morch, 1860. 



Adult shell adherent, spiral, solitary or clustered ; aperture 

 slightly inflexed above, very obsoletely effused below, without 

 internal lamellae. Operculum slightly concave, arctispiral, fur- 

 nished with long divergent multifid setae. Recent and fossil. 



The shells are generally very small, and usually so tender as 

 to be very rarely found fossil in a good state of preservation. 

 Difficult to distinguish from Vermiculus. 



Subgenus BURTINELLA, Morch, 1861. 



Young shell adherent, the adult free, thick, widely conically 

 elevated, trochiform or planorboid, usually sinistral, rarely clex- 

 tral, last whorl protracted, more or less prolonged, tubular 

 within, angular exteriorly, aperture circular, not contracted. 

 Fossil only, 15 species. Oolitic, Cretaceous, Tertiarj- ; Europe, 

 India. 

 B. CONCAVA, Stol. (Struc. and Syst. Conch., t. 67, f. 69, 70). 



Subgenus TUBULOSTIUM, Stoliczka, 1868. 



Shell planorboid to broadly conical, aperture contracted, pro- 

 longed in a tube. 4 sp. Jurassic, Europe; Cretaceous, India ; 

 Tertiary, United States. 



