THE NATURAL HISTORY SURVEY. 95 
under surface of the connecting plate, large, deeply excavated; 
pallial line deeply impressed anteriorly; cavity of the beaks 
deep; nacre silvery white, only slightly iridescent. 
Length, 117.50; height, 70.00; breadth, 51.50 mill. J (9819). 
o OF O0r7 65.00; se 41.50 " © (8054), 
4) RE OOs eh! 73.00; as AS a0 © (12425). 
ee cleyes ear oe 93.00; Dt 62.00) 2u 3 (coll. Jensen). 
aa POE Oke eh 72.00; os BoLOOs Q ae sis 
Animal: Generally pearly white or flesh colored; anal and 
branchial openings of moderate size, both papillose; ctenidia 
long and wide, rounded before, pointed behind, strongly lami- 
nated, united above and to the opposite pair throughout their 
entire length; labial palpi long, wide, tongue shaped, united at 
base, light pearly or flesh colored; foot large and muscular, 
flesh colored; abdomen pearly and iridescent; mantle pearly 
white, edged with brown; siphons yellowish white inside, edged 
with blackish brown; in all of the specimens examined by the 
writer the posterior part of the abdomen was supplied with a 
small triangular appendage of unknown function; liver dark 
brown; heart pulsations regular, seventeen to eighteen per 
minute. The posterior half of the outer branchium is used as 
a marsupium. 
Distribution: New York west to Iowa, southern Canada 
south to Louisiana. 
Geological distribution: Pleistocene. 
flabitat: In lakes and rivers of some size, generally on a 
muddy bottom. 
Remarks: A very distinct species, like no other in the 
region, the peculiar slope of the posterior portion of the shell 
at once distinguishing it. The female is more produced pos- 
teriorly than the male, the latter having the posterior end much 
sharper, and also having a peculiar bulge in the ventral part of 
the shell, just posterior to the center. The rays vary from very 
narrow threads to wide bands and are placed differently from 
any other species. It seems to be rather widely distributed in 
the area,and is fairly common. Aspecimen from the Little Calu- 
met River, collected by Mr. Jensen, weighed one pound and one 
and a half ounces when alive. 
27. Lampsilis multiradiatus Lea, pl. xxi, figs. 2, 3. 
Unio multiradiatus Lea, Trans. Amer. Phil. Soc., Vol. III., p. 409, pl. ix., 
fig. 15, 1829. 
Shell: Subovate, of medium size, rather solid, inflated, 
