THE NATURAL HISTORY SURVEY. 83 
abdomen; ctenidia short and wide, rather pointed behind, 
rounded before, the inner ctenidium the larger, united above 
throughout their entire length; labial palpi large, elongately 
oval or tongue shaped, united as is usual in this genus; foot 
large and muscular; pulsations of the heart very regular, eleven 
to twelve per minute. Four gills used as marsupia. 
Distribution: New York and Georgia west to Kansas and 
Dakota, Michigan south to Texas. 
Geological distribution: Pleistocene. 
Habitat: Sameas that of Unio gibbosus. 
Remarks: ‘The writer has noted the principal differences 
between this species and A/icata under the latter species. There 
was considerable variation among the specimens of this species 
examined. The second cardinal in the right valve may be 
almost half as large asthe posterior cardinal or it may be 
absent; there is also every degree of undulation, from a condi- 
tion almost smooth (9347) to one in which the ridges are large 
and finely developed. Unio pilsbryi Marsh seems to be founded 
on one of these variations. This is a rather common species and 
is widely distributed, being found in most parts of the area. It 
has been found fossil in a cellar dug on the corner of Frederick 
and North Clark Streets, about half a mile fromthe present lake 
shore. Very large and fine specimens weighing 1 lb. 10 oz. 
have been collected by Mr. Jensen in the Little Calumet River. 
The specimens from this locality are very rugose and. show a 
tendency toward Q. mu/tiplicata. 
GROUP OF QUADRULA LACHRYMOSA. 
20. Quadrula lachrymosa Lea, pl. xxiv., fig 1; pl. xii., fig. 2. 
Unio lachrymosus Lea, Trans. Amer. Phil. Soc., Vol. III., p. 272, pl. vi., 
fig. 8, 1827. 
Unio asperrimus LEA, Trans. Amer. Phil. Soc., Vol. IV., p. 71, pl. v., fig. 
3, 1880-1. 
Unio guadratus, RAFINESQUE, Say, Amer. Conch., pl. lii., 1834. 
Unio lunulatus Pratt, Proc. Davenport Acad. Sci., Vol. I., pl. xxxi., fig. 
1, 1870. 
Shell: Quadrate, compressed, solid and heavy, pustulose; 
rounded before and squarely truncated behind; dorsal margin 
straight or slightly curved; ventral portion with an excavation 
near the posterior end; surface roughened by growth lines and 
covered with pustules which are arranged in two series on either 
side of a smooth depression situated in the center of the shell, 
and extending from the umbones to the ventral border, at the 
