XXU / 



"Say's Melania armigera (and also Lea's 3T. Duttoniana and 

 M. catenoides) belongs to Rafinesque's genus Pleurocera, in 

 which there is a short, straight canal anteriorl}', and when this 

 canal is lengthened, as in Fusus, the genus lo, of Lea, is the 

 rcsnit. 



'•'• Strepoma of Rafinesque (or Ceriphasia of Swainson) are 

 slightly different forms, in which the aperture and tlie vertical 

 plate formed by the anterior portion of the whorls, bear some 

 resemblance to the same parts in Cerithium telescopium." 



In October, 1840, Prof. Haldeman published a 

 supplement to his "Monograph of the Limniades," 

 containing, among other matter, the following pro- 

 posed 



'* Subgenera of Anculosa. 



" AncuJosa, Say. — Substance of the shell thick and beav}', 

 labium much thickened. 



'■^ Lithasia, Hald. — Shell heavy, having protuberances; aper- 

 ture with a notch in the nacre above and below. 



^^ Paliidomus, Swains. — Shell smooth, margin of the outer 

 lip creuated, labium very thick and enamelled. 



'■'■ Hemimitra, Swains. — Like Paludomus^ but with coronated 

 whorls. 



" Mudalia, Hald. — Shell smooth, thin in texture, labium 

 without enamel." 



In his description of a species of Anculosa pub- 

 lished upon the same occasion, Prof Haldeman refers 

 to "Paludhia {Mudalla) dissimilis, Say," so that 

 there can be no doubt as to the section of Anculosa 

 indicated by the subgenus 3Iuclalia. On the cover 

 of No. 2 of the monograph (January, 1841) is the 

 description of " subgenus- Angitrema. Shell spinous, 

 aperture subrhomboidal, with an anterior sinus. Ex. 

 3Idania c(rmige7^a, Say." 



I adopt Angitrema as a genus, with Llthasia as a 

 subgenus of it. Mudalla cannot stand in the sys- 

 tem, because its characters are not constant, Anc. 

 dlsslmllls having frequently a heavy dej)Osit of nacre 

 on the columella. 



Mr. Lea has described several new genera of 

 shells eliminated from the American 3Ielanlce. He 

 early recognized in Mr. Say's genus Anculosa a good 



