112 AMERICAN JOURNAL 



Ohio,— C. crassula. Four whorls of the spire reversed? apex 

 acute, shell thick, mouth more than half the total length." 



Messrs. H. & A. Adams, with very doubtful propriety, refer 

 this genus to Melanopsis. Prof. S. S. Haldeman, in an article on 

 Mollusca, contributed by him to the American edition of 

 Heck's Iconographic Encyclopaedia, li. p. 84, remarks that 



" Say's Melania armigera (and also Lea's M. dvttoniana 

 and M. catenoides) belongs to Eafinesque's genus Pleurocera, 

 in which there is a short, straight canal anteriorly, and when 

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

 the result. 



" Strepoma, of Eafinesque (or Ceriphasia, of Swainson,) are, 

 slightly different forms, in which the aperture and the vertical 

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

 resemblance to the same parts in Cerithium telescopiumJ^ 



In October, 1840, Prof. Haldeman published a supplement 

 to his " Monograph of the Limniades," containing, among 

 other matter, the following proposed 



"Subgenera of Anculosa. 



" AncuJnsa, Say. — Substance of the shell thick and heavy, 



labium much thickened. 

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

 ture with a notch in the nacre above and below. 

 " Pahidomus, Swains. — Shell smooth, margin of the outer lip 



creuated, labium very thick and enamelled. 

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



whorls. 

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

 out enamel." 

 In his description of a species of Anculosa published upon 

 the same occasion, Prof Haldeman refers to '■' Paludlna 

 [Mudalia) dissimilis, Say," so that there can be no doubt as to 

 the section of Anculosa indicated by the subgenus Mudalia. 

 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. Melania 

 armigera^ Say." 



I adopt Angitrema as a genus, with Lithasia as a subgenus 

 of it. Mudalia cannot stand in the system, because its charac- 

 ters are not constant, Anc. (i^.ssm^7^5 having frequently a heavy 

 deposit of nacre on the columella. 



Mr. Lea has described several new genera of shells elimi 

 nated from the American Melanise. He early recognized in M r. 

 Say's genus Anculosa a good natural genus, and adopted it 

 in his descriptions. In Philos. Trans. Yiii. p. 163, he pro- 

 posed to separate the species of Melania according to certain 



