LEPTON. 193 



All the KelliidcB are of small size. They are also 

 upstarts in a conchological point of view, none having 

 been known to Linne, or described by any writer until 

 near the close of the first decade of the present century. 

 But the family came into this country long before the 

 Conqueror. Many of our recent species flourished in 

 the time of the Coralline Crag ; and the history of their 

 existence in these dark and remote ages has been duly 

 chronicled. They now inhabit both hemispheres : one 

 kind of Montacuta is found in the Arctic seas, and 

 species of that and other genera are diffused over all the 

 vast tract of sea which lies between Cape Horn and 



" The gulfy coast of Norway ironbound." 



A peculiarity of this family consists in some of them 

 being viviparous. This is certainly the case with Mon- 

 tacuta substriata, Lasaa rubra, and Kellia suborbicu- 

 laris. The Sphariida? resemble these members of the 

 present family in the above-mentioned peculiarity, as 

 well as in shape. 



Genus I. LEPTON * Turton. PI. IV. f. 7. 



Eodt voluminous : mantle protruded, and furnished with 

 long tentacular cirri : foot capable of being expanded into a 

 disk -like form. 



Shell roundish-oval or triangular : cartilage small : hinge 

 furnished with a single cardinal tooth and two strong lateral 

 teeth in each valve. 



This genus closely resembles Galeomma ; but the 

 animal has no ocelli, the shell does not gape in front, 

 and the hinge exhibits a goodly array of cardinal and 

 lateral teeth. Mr. Clark has, by his careful observa- 

 tions, completely dispelled the commonly received idea 



* Tliin as a scale. 



