FAMILY 12. CONVOLUTA. 257 
curva, plicis magnis, acutis ; labro tenui, simplici, acuto, nunquam 
reflexo. 
The Cymbe or ‘‘ Boat-Melons”’ are chiefly distinguished from the Me- 
lones or ‘‘ Simple Melons” by the sudden concave angular depression of 
the upper part of the whorls; a kind of sutural shelf as it were is in 
fact thus formed around the upper portion of the spire, so as to obliterate 
in many instances all external trace of the apex. 
Having detailed the history and origin of this genus in our observa- 
tions on Melo, it only remains for us to describe the shell of Cymba as 
being of rather large size, smooth, oblong, or ovate, very ventricose, emar- 
ginated at the base, and sometimes covered with a kind of glazed vitreous 
pellicle ; the spire is very short, with the apex rude, and occasionally 
obsolete ; the aperture is sometimes ovate, sometimes elongated ; the 
columella is curved, with the plaits large and acute, and the lip is thin, 
simple, and never reflected. 
Example. 
Pl. CCLXXXIV. 
Cympa Neprunt, Broderip. Sowerby, Species Conchyliorum, Part [. 
p. 5. fig. 2. a, b, c,d. Martini, Conch., vol. iii. pl. 71. f. 767. En- 
cyclopédie Méthodique, pl. 386. f. 1. 
Patera Neptuni, Martini. 
Voluta Neptuni, Lamarck. 
Family 12. CONVOLUTA. 
Testa ad basin emarginata, anfractibus confertim volutis, non descenden- 
tibus. 
This interesting and highly esteemed group, constituting the last of the 
creat series of pectinibranchiate gasteropods, was introduced by Lamarck 
