316 ANNALS OF THE CARNEGIE MUSEUM. 
generally more or less injured.*® Anal large, with crenulations. 
Branchial large, with papillae; toward the front papillae gradually 
changing to crenulations, which soon disappear, so that the anterior 
inner edge of the mantle is smooth. Palpi of usual shape, but small; 
their posterior margins united for about one-half, or less, of their 
length. 
Gills conforming to the shape of the shell, rather short and broad, 
the inner much the wider anteriorly. The anterior attachment of 
the gills is as usual. Gill-diaphragm normal. Inner lamina of inner 
gills free from abdominal sac, except anteriorly, where it is connected for 
about one-third to almost one-half of the length of the abdominal sac. 
Fic. 18a. Gravid female, medium size (shell 55 mm. long), from Cumberland 
River, Eadsville, Wayne Co., Ky. (Carn. Mus., No. 61, 4,968.) 
Gills with well developed water-tubes and septa. Those of the male, 
and the non-marsupial gills of the female, with distant septa and wide 
water-tubes. Marsupium formed by the posterior section of the outer 
gill; more than half of the gill takes part in it; a larger section in 
front and a smaller behind remain non-marsupial. The marsupial 
part bulges out considerably beyond the original edge of the gill, 
about as wide again as the gill, and in this section the septa are much 
more crowded, and the ovisacs are narrow. When gravid, the ovisacs 
swell only slightly, so that they are very little compressed, and chiefly 
so near their base. The placente have the same subcylindrical and 
only slightly compressed shape. Practically the whole of each ovisac 
39 But in some it was positively absent. This is also a rather primitive condition, 
not observed in any*other form of the Lampsiline. 
