m 



NAIADES OF MISSOURI 67 



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. 



c? 105 X 40 X 34 0.190 (White R., HoUister — ) 

 9 108 X 40 X 39 0.190 (Center Cr., Webb City) 



? 75 X 30 X 28 0.200 (St. Francis, Greenville) 



cf 70 X 28 X 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 imique shell and yet it may well be described as an 

 extremely elongated 0. metanevra. The breeding record kept by 

 the writer is early embryos August 14 and sterile maruspia August 

 29; Wilson and Clark (191 1, p. 42) record its gravidity for June 

 17 and July 27 but do not indicate the embryonic stages. 



Genus Rotundaria Rafinesque. 



(Type Ohliquaria [Rotundaria] tuber culata 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., XXIL 



p. 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, acutni- 

 nate postero-ventrad; only outer gills marsupial water tubes 

 more crowded than in non-marsupial 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. 



