MELANITHES. 187 



MEGARIMA. Rafinesque. A genus proposed to include species 

 of Terebratula, Auct. which are smooth and nearly equivalve. 

 T. lsevis, T. crassa, T. truncula. 



MEGASPIRA. Lea. (Meyag, megas 3 great, and spire.) M. Ru- 

 schenbergiana, (fig. 294) is a pupiform land shell remarkable for 

 the length of its spire, which consists of no less than twenty-five 

 close set, narrow, gradually increasing whorls. The outer lip is 

 simple, slightly thickened ; the inner lip has a tooth on the body- 

 whorl, and two folds on the columella. Only one species of this 

 singular shell is known. 



MEGATREMA. Leach. A genus composed of those species of 

 Pyrgoma, Auct. which have a large aperture. Fig. 33. 



MELACANTHA. Sw. A sub-genus of Melania. Sw. p. 341. 



MELAFUSUS. Sw. A sub-genus of Melanopsis. Sw. p. 34 1 . 



MELAMPUS. Montf. Conovulum, Lam. A genus composed 

 of species of Auricula, Auct. of a conical form. A. conoidalis, 

 fig. 298. 



MELANIA. Auct. (MeXae, melas, black.) Fam. Melaniens, Lam. 

 Ellipsostomata, Bl. — Descr. Turrited ; spire generally elongated, 

 acute ; aperture entire, oval or oblong, pointed at the posterior 

 extremity, rounded anteriorly, with a kind of indistinct canal or 

 sinuosity : epidermis thick, generally black. — Obs. In common 

 with other fresh-water shells, the Melanise are frequently found 

 with corroded apices. This genus is known from Melanopsis by 

 the absence of the notch at the anterior part of the aperture. 

 The Melaniae occur in rivers of warm climates. The fossil species 

 are frequent in upper marine formations. Fig. 313, M. subulata. 



MELANIANA. Lam. (Melaniens.) A family belonging to the 

 first section of the order Trachelipoda. The genera contained in 

 it maybe distinguished as follows. 



1. Melanopsis, Aperture notched ; columellar lip thickened 



above; including Pirena. Fig. 315, 316. 



2. Melania. Aperture not notched ; columellar lip not thick- 

 ened ; including Auculosa, Pasitk&a, Io. Fig. 313, 314,317- 



MELANITHES. Sw. A sub-genus of Melanopsis. Sw. p. 341. 



