108 



II. H1PPONYCINJE. 

 Genus HIPPONYX, Defrance, 1819. 



Shell thick, obliquely conical, non-spiral, apex somewhat pos- 

 terior and directed backwards, surface rugose or longitudinally 

 grooved or cancellated ; muscular impression horse-shoe shaped ; 

 base of attachment (opercular piece) when present, thick. 



Animal oval or suborbicular, conical or depressed ; foot very 

 thin, a little thickened towards the margins ; head globose, sepa- 

 rated from the body by a neck-like constriction ; eyes upon 

 swellings of the tentacles. 



Dentition, PL 30, fig. 6. 



Distribution : Warm seas. Fossil : Cretaceous, Eocene. U. S., 

 Europe. 



The synonyms are Cochlolepas, Klein, 1753; Krebsia, Morch., 

 and Amallhea. Schum., 1817. 



The same species will either excavate a cavity to which it 

 adheres, or secrete a testaceous support. The section Amalthea 

 was formed for certain species which were supposed to differ 

 from Hipponyx in not secreting a shelly base, but forming 

 instead a cavity in the surface of shells. . . 



Genus MITRULARIA, Schum., 1817. 



Shell conical, more or less irregular with a subcentral, sub- 

 posterior, subspiral apex ; interior with a central, half cup-shaped 

 lamina, open in front, free on the sides, attached at the apex ; 

 basal plate thickened. 



Animal with broad muzzle, tentacles lanceolate, with eyes 

 externally near their base, the neck lobed on either side. 



Inhabits temperate and tropical seas, distribution world-wide. 

 The synonymy includes Cemoria, Risso ; Mitrella, Trochilina, 

 Trelania and Poculina, Gray, 1807; Lithedaphus, Owen, and 

 Calyptraea, Lam., 1801, not 1799. Lamarck at the later date 

 adopted for his type a species belonging to the present group to 

 which it has since been generally applied, whilst the name of 

 Galerus, Humphrey, has been the received designation for the 

 Calyptraea, Lam., of 1799. I follow Dr. Fischer in correcting 

 this matter, and like him displace the earlier but ill-founded 

 name of Humphrey for the latter. 



