OF CONCHOLOGY. 101 



Ceriphasinse^ tlie rcloption of which would still leave our 

 species in connection as a subfamily with shells to which 

 they are not at all closely related. 



In endeavoring to eliminate, from the rather confused 

 synonymy, generic and subgeneric groups of Strepomatidx, 

 some difficulty is encountered at the threshold, on account of 

 the various opinions held by the different naturalists who have 

 studied them, regarding the relative importance which should 

 be assigned to various characters of the shell, in constituting 

 these divisions. 



The genus Hemisinus, Swainson {Basistoma, Lea,) belongs 

 to Mr. Gill's family Melanopidoe. The little Paludomus brevis, 

 D'Orb., of the West Indies, is apparently the American repre- 

 sentative of an exotic genus ; the large tuberculate Melanians of 

 Central America, and the smooth Pachyche-ili of that country 

 and of Mexico, probably do not belong to our family 

 Strepomatidse. 



Thus the range of the species of the family may be con- 

 sidered as restricted within the borders of the United 

 States.* 



Swainson formed the following curious generic system for 

 the shells under consideration :— f 



Family TURBID^. 



(Subfamilies ArnpullirinDe, Melanianse, Turhinae, Janthinse) 



Subfamily MELANIANS. 



Genus Paludomus, Swainscn. 



Subgenus Anculosa, Say. 

 Genus Melania, Lam. 



Subgenus Hemisinus, Swainson. 

 Genus Melanopsis, Lam. 



Subgenus Melafusus, Swainson. 

 Subfusiform, the base contracted, and the aperture and 

 spire nearly equal. 1 species. America. (= lo.) 

 Subgenus Melatoma, Swains. 



Fusiform, longitudinally ribbed; a deep sinus at the top 

 of the outer lip ; base contracted, channel wide. M. 

 costata. (This species, mistaken by some for our genus 

 Schizostoma, is actually an exotic marine shell = genus 

 Glionella?) 



* Three or four are estra-limital, inhabiting Cuba and Mexico ; but these 

 do not constitute one per cent, of the whole number of species, 

 t Manual of Malacology, 1840. 



