Hannibal: californian freshwater molldsca. 195 



Idiopoma (Cipangopaludina) malleata (Reeve). 



"i Pahidina lata, von Martens, 1860; P. malleata, Reeve, 1863; 



P. ^ Japonica, Mart.', Wm. Wood, 1892 ; Vivipara ^ stelmaphora, 



Bgt.', Stearns, 1901; V. ^ kcythoides, Benson', Hannibal, 1908. 



Shell large and very broad, spire elevated-conic, apex large and 



sub-prominent, sutures impressed, whorls inflated and fairly deep, 



marked by four revolving lines of punctures, two above, one at, 



and one below the periphery, an obtuse carina in early stages which 



is entirely lost before the adult condition is reached, axis perforate, 



aperture nearly as broad as high ; habitat quiet streams and marshy 



situations. 



Japan : introduced in Coast Range System. 



Family LIOPLACID^, Gill, 1871. 



Shell large, averaging 25 mm. in altitude, elevated-conic, covered 

 with a greenish or brownish epidermis, whorls more or less appressed 

 and shouldered, aperture sinuate, operculum uniformly thin and 

 iiorny, annular, but with a sub-spiral nucleus; animal small, foot 

 large, quadrate, and produced in front of head, rostrum small, 

 branchial laminse elongate-triangular, of equal size, and arranged in 

 a straight row, cervical lappets not forming tubular ducts ; habitat 

 streams, less frequently lakes. 



This group, even to late years included in the YiviparidDe, from 

 which it differs in numerous details, compi'ises two genera, Lioplax 

 and Campeloma, Rafinesque {-\-Ambloxis, ' Rafinesque,' Binney, 

 '■ MelantJto, Bowditch,' Binney). The family appears to be a decadent 

 one. While fossil species are fairly numerous and indicate a dis- 

 tribution as far west as California in early Tertiary times, at present 

 Lioplax contains only the solitary species L. siibcarinata, Say 

 { + cyclostomatiformis , Lea), and Campeloma embraces but two, decisa, 

 Say (-{-coarctata, Lea, rufam, Hald., subsolidiitn, Anthony, Milesi, 

 Lea, etc.), and crassida, Raf. {-\-ponderosa, Say). 



The presence of a sub-spiral nucleus to the operculum in these 

 genera is interesting from the light it throws on the origin of 

 concentric operculi in groups derived from sub-spirally operculate 

 ancestors, the annular later growth appearing as an acquired 

 character. 



Genus Lioplax, Troschel. 



Lymncea (sp.). Say, 1817 (Z. stihcarinata, Say); Paludina (sp.). Say, 

 1819 (Z.. siihcarinata, Say); Helix (sp.), Wood, 1828 {11. decisa, 

 Wood = L. stibcartnata, Say) ; Lioplax, Troschel, 1857 (Z. sub- 

 car inata, Say); Haldemania, Try on, 1862 (Z. subcar inata, Say). 

 Type, Lymncsa subcarinata, Say. 



Shell small, averaging 20 mm. in altitude, attenuate-conic, sub- 

 perforate, whorls inflated and rounded, more or less shouldered at 

 periphery, aperture sinuate and retracted below, peristome complete; 

 habitat lakes and streams. 



