249 



A great many shells of this species have been seen from time to time from 

 various places in Indiana. Very many of them, as this one well does, pre- 

 sent a peculiar diseased or pathologic condition of the cardinal teeth not alto- 

 gether unlike the condition exhibited by the interior surface of Margarita na cal- 

 ceola. In this instance the cardinal teeth are nearly destroyed and are represented 

 by distorted and imperfect vestiges. It would be interesting indeed if the Station, 

 during the next season, could investigate this phenomenon as a study in the 

 physiology of Unio, a field yet uncultiva'ed. 



Unio rubiginosus Lea. Two specimens from Turkey Creek, one of which is 

 pathologic 



These shells are intermediate between Unio trigoniis Lea and typical Unio 

 rubiginosus Lea. They are somewhat more trigonal than the latter shells are com- 

 monly found, and, on the other hand, are less heavy and trigonal than the ponder- 

 ous river form. The whole group is sadly confused and needs painstaking revision. 



CORBICULADiE. 



Sphcerium rhomboidenrn Prime. A single specimen only was taken, from Turkey 

 Lake, in muddy bottom and in comparatively deep water. The specimen is very 

 much thinner than usual. 



Sphcerium solidulum Prime. Ten specimens from Turkey Lake. These are 

 all smaller than common and quite heavy; they came from the beach at Vawter 

 Park. 



FRESH-AVATER UNIVALVES, 



Amnicola porata Say. Eight specimens of this small univalve were obtained 

 in Tippecanoe Lake. Neither it nor others of tiie univalves found present any 

 characters different from shells found in streams throughout the State. 



Campeloma decisinn Say. Five dead specimens from Turkey Lake. 



Campcloma integrum Dekay. One dead specimen from Turkey Creek. 



Cavipeloma rufum Haldeman. About twenty specimens from Tipj^ecanoe 

 Lake; tiiirteen, one of which was reversed or sinistral, from Turkey Creek. 



There is no difficulty in recognizing these several forms, though tyros an- 

 nually make the discovery that there are no valid species but one. C'ampeloma 

 rufum differs from both the others constantly by the outlines of the whorls, the 

 shape and color of the aperture, the pink character of the apical whorls, a feature 

 which is best illustrated in the very young and which is a constant character, and 

 in the polished epidermis, which presents a character seen in no other member of 

 the genus. Reversed forms are not uncommon, but yet may be justly considered 



