THE NAIADES OF MISSOURI 5 31 
Nn 
3. Proptera—Lampsilis-Group. In this division the best 
adaptation for the proper respiration of the embryos is secured 
by situating the numerous, dilated ovisacs in a more or less kidney- 
shaped marsupium near to the branchial opening where the 
postero-ventral margin of the mantle is set with papillae, flaps, 
etc. The first members of this group have this mantle edge only 
slightly crenulate and lamellate, while beyond the genus, Pro- 
tera, is the culmination of the modern structure in the arrange- 
ment of the inner edge with papillae or flaps close to, or remote 
from, the outer edge. This group is represented by about thirty 
species in this State. 
It may be added that the Lampsilinae are dissimilar to the 
Umnioninae in their breeding season in that practically all the 
species are long period breeders (bradytictic), but that the glochi- 
dia of these two sub-families are similar in form and in being spine- 
less. It is especially to be noted that the members of these two 
sub-families have developed perfect hinges in the adult shell, 
whereas those of Anodoniinae possessing glochidia with spines 
have defective hinges. We should also note that the Lampsilinae 
are able to spread their valves far apart—a habit which may 
have some relation to the differentiation of their mantle margins 
in admitting greater incurrents of water—while the Unzioninae 
and Anodontinae show a primitive character in being unable to 
force their valves far apart and accordingly in not developing 
stronger papillae and more extended mantle edges at their siphonal 
openings—a defect that may be somewhat counterbalanced by 
the delvelopment of larger palpi than is very often seen in the 
Lampsilinae. It may be stated further that there is not such 
intergradation of forms in this sub-family as seen among the 
Umioninae, or even as noticed among the Anodontinae as there 
seems to be more distinctness and fixity of characters among the 
several genera, especially as seen in the marsupial structures 
upon which a good key is built. 
Genus Ellipsaria Rafinesque. 
1820—Ellipsaria Rafinesque, Monog. Biv. Shells of R. Ohio., Ann. 
Gen. Sci. Phys. 
1900b—Ptychobranchus Simpson, Proc. Ac. N. Sci. Phila., p. 79. 
(Type, Ellipsaria fasctolaris Rafinesque 1820 = phaseolus 
Hildreth, 1828). 
