MARGIN EL LA, 



Date Shell. 



Generic Character. 

 Tetta ovafa. Spira brexissima aut iiuUa. l,abium exterius crassissimum, 

 margiue interiore crenato. Columella plicata. Basis subiiitcgra. 

 Anhnat aijnlatum, capitis fronte profunde emarginato ; oculis ad 

 tentaculurum 2 subulutorum basin externam adsitis ; tuba Jugulari 

 simplici ; pede magna, foliaceo, pone attenuato ; penuld dilatatd, 

 testce latera obtegente. 

 Typ, Gen. Volutce perspicula, glabella, prunum, S^^c. Lin. 



Shell oval. Spire very short or concealed. Exterior lip very thick, 

 with the internal margin crenated. Pillar plaited. Base nearly 

 entire. Animal capitate ; head notched in front, with length- 

 ened, pointed tentacula, at the external base of which are the 

 eyes ; neck with a simple tube ; foot large, foliaceous, pointed 

 behind ; mantle dilated, and folded over the sides of the shell. 

 Generic Types Vol. perspicula, glabella, prunum, SfC. Lin. 



-LiAMARCK first separated the shells comprised in this genus 

 from the Volutes of Linnscus ; their principal distinction rests 

 in the formation of the outer lip, which has a very thick 

 margin, more or less toothed on the inner rim ; the base 

 likewise is nearly entire, and the inner lip quite wanting. 



By these peculiarities, the Date Shells are easily known 

 from the Volutes on the one hand, and the Cowries on the 

 other ; and the invaluable researches of M. Adanson, who 

 has described and figured the animals of each of these 

 genera, has established this distinction on the most solid 

 principles ; it will, however, be interesting to trace, by the 

 shells only, how beautifully this arrangement is developed. 



The Marginellce may be divided into two sections ; the 

 first bearing; in form and habit a strono- resemblance to the 

 Ci/prace, and the second gradually losing these mdications, 

 and acquiring those of the spiral Volutes. Among the first 

 are several species, which, like the Cowries, appear destitute 

 of any spire (as in M. cingulata) ; this part, however, begins 

 to show itself in other successive species very progressively, 

 until it becomes elevated and defined in M. glabella. This 

 shell may be considered the passage to the second division, 

 in which the species lose the simple oval form of the first, 

 and acquire a contracted base and pointed spire, perfectly 

 resembling Valuta undulata La7n. and its allies. The ex- 

 treme developement of these characters is shown in M.faba. 



This genus must, then, be considered as connecting those 



of Cypraa and Voluta (Lam.) ; excepting one, the whole of 



the species are very small ; and as the three here selected 



to illustrate these remarks are frequently seen, and have 



PI. 9r. 



