12 NATICnXffi. 



Subgenus MARSENINA, Gray, 1850. 



Shell auriform, similar to Lamellaria. 



Animal (PL 1, fig. 20) with shield only partially covering the 

 shell, open in the middle, the anterior margin deeply incised a 

 little to the left of the middle, and again incised at the middle 

 of the right margin. Dentition, PL 1, fig. 10. Boreal Seas. 

 L. prodita, Loven. Colobocephalux, Sars, is a synonym. 



Genus ONCIDIOPSIS (Beck), Bergh, 1853. 



Shell internal, membranous, flexible, slipper-shaped, nut spiral, 

 oblong, obtuse at the extremities. 



Animal (PL 1, fig. 21) completely enveloping the shell ; dorsal 

 shield verrucose, thick, margin entire ; foot elongated, lanceo- 

 late, exceeding the shield at either extremity ; tentacles cylin- 

 drical, with eyes at their exterior bases. Dentition as in Velutina 

 (PL 1, fig. 11). Boreal Seas. 0. glacialis, Sars. 



? Genus CALEDONIELLA, Souverbie, 1869. 



Shell heliciform, imperforate, oval, orbicular, thin, invested by 

 a thin epidermis which extends beyond the lip ; spire much 

 depressed, sublateral ; whorls few, rapidly increasing ; aperture 

 oblique, rather large, the extremities of the simple lip united by 

 a callus extending widely upon the whorl. Animal unknown. 



C. Montrouzieri, Souverb. New Caledonia. 



Genus VELUTINA, Fleming, 1822. 



Shell thin, mostly external, calcareous, auriform, paucispiral, 

 invested *by a velvety epidermis ; spire lateral, suture well im- 

 pressed ; aperture large, rounded, the lip thin, the columellar 

 lip a little reflected. No operculum. 



Animal with large oblong foot; margin of mantle developed, 

 and more or less reflected over the edge of the shell ; head 

 broad ; tentacles subulate, blunt, far apart, with eyes on prom- 

 inences at their outer bases. 



Dentition, 2-1-1-1-2, the central tooth subquadrangular, multi- 

 cuspid, the central cusps ve^r long and sharp ; lateral teeth 

 multicuspid, marginals narrow, with a few obsolete denticles on 

 the margin (PL 1, fig. 8). 



