NAIADES OF MISSOURI 149 
in metanevra) with green toothed splotches pointed ventrad. 
INTERNAL STRUCTURES:—Cardinals double in both valves, 
serrated and irregular; laterals slightly double and very long; 
interdentum unusually long; nacre white subject to stain. 
Sex Length Height Diameter Um. ra. Locality. 
CO MOSh, Xa AOl eXa7-3)4. 0.190 (White R., Hollister—) 
OM LOS) Lar 40 39 0.190 (Center Cr., Webb City) 
OTe x | ao 28 0.200 (St. Francis, Greenville) 
GH On ak 2S 26 0.210 (Black R., Williamsville) 
MISCELLANEOUS REMARKS;—It is regretted that the descrip- 
tion of this interesting species still remains incomplece, from the 
fact that no juveniles, nor mature individuals bearing ripe glochidia, 
are found yet. Cylindrica is distinctly a southern species and is 
not found in North or even Central Missouri and is never found in 
the Mississippi north of the mouth of the Missouri. It is a rather 
common shell for the White and St. Francis Rivers and from 
deposits of shells in Indian graves it has been found to be abundant 
in the streams of Southwest Missouri where it is now extinct. 
Perhaps the identity of cylindrica is one of the most evident 
because of its unique shell and yet it may well be described as an 
extremely elongated Q. metanevra. The breeding record kept by 
the writer is early embryos August 14 and sterile maruspia August 
29; Wilson and Clark (1911, p. 42) record its gravidity for June 
17 and July 27 but do not indicate the embryonic stages. 
Ka Bed os 
Genus Rotundaria Rafinesque. 
(Type Obliquaria [Rotundaria] tuberculata Rafinesque.) 
1820—Rotundaria Rafinesque, Monograph of Bivalve Shells of River 
Ohio, Ann. Gen. Sci. Phys. Brux. 
1900b—Rotundaria (Raf.) Simpson, Proc. U. S. Nat. Mus., XXII, 
Pp. 794 (as subgenus) 
ANIMAL CHARACTERS :—Siphonal openings peculiar in possess- 
ing no true supra-anal openings; gills short wide, inner much 
wider centrally, inner laminae free from visceral mass; palpi 
connected about two-thirds of their length antero-dorsad, acumi- 
nate postero-ventrad; only outer gills marsupial water tubes 
more crowded than in non-marsuplal gills when gravid marsupia 
not much distended length-wise through center, ventral edge 
pointed; conglutinates white, broken, rather narrowly leaf-like, 
or lanceloate; glochidia semi-elliptical, spineless, large, hinge 
line short and undulate. 
