298 ANNALS OF THE CARNEGIE MUSEUM. 
Alasmidonta and Strophitus. It has the beak-sculpture® of the genera 
of the Alasmidonta-group, and approaches Strophitus in the hinge. 
It is very much to be regretted that gravid females are not at hand, 
and that the structure of the charged marsupium and the glochidia 
remain unknown. The sterile females, which I have seen, make 
it clear that only the outer gills are used as marsupia, and that they 
havea structure like that found in sterile females of the Anodontine 
in general. 
Lastena lata (Rafinesque). 
I have received, from B. Walker, the soft parts of two males and 
two sterile females from the Cumberland River in Pulaski and Cumber- 
land Cos., Kentucky. 
Anal and supra-anal separated by a rather short connection of the 
mantle. Anal finely crenulated, branchial with papillae. Posterior 
margins of palpi connected for a short distance. 
Gills and gill-diaphragm normal, and not as described by Simpson,* 
Gills long and rather narrow, the inner one decidedly wider in front, 
its anterior end distinctly in front and below the anterior end of the 
outer gill, but separated from the palpi by a short, but distinct interval 
(it is connected with the descending part of the mantle attachment 
line for about three-fourths of its length, while one-fourth is occupied 
by the interval). Posteriorly, the gills do not project freely, but are 
entirely of the usual shape. Inner lamina of inner gills free from the 
abdominal sac with exception of the anterior end. 
Septa and water-tubes normally developed. Marsupium formed 
by the outer gills, with the water-tubes narrow, and the septa close 
together, thick, and with strongly wrinkled epithelium. In the females 
at hand, no indications of secondary water-tubes could be seen. The 
thickened tissue at the edge of the gill was also not well developed. 
Both specimens are small (under medium size, about 40 and 45 mm. 
long), and seem never to have been gravid. 
Color (of alcoholic material) whitish, edge of mantle brown, black 
behind. 
30 This sculpture is somewhat variable. It begins with simple concentric bars 
upon which a few heavier bars follow, slightly sinuated in the middle and angled 
behind, and then follow a few more upon the disk, quite heavy, but indistinct. 
The latter are sometimes absent, and sometimes even the sinuated bars are very 
rudimentary. The sculpture resembles somewhat that of Strophitus. 
31 Simpson (1900), p. 654) says: “inner and outer (gill) about alike in size and 
form, projecting free slightly behind.” 
