66 NAIADES OF MISSOURI 



its external and internal shell structures are identical with those of 

 0. metanevra. 



Sex Length Height Diameter Locality 



^ 9 86 X 70 X 54mm (Des Moines R., Dumas) 



Miscellaneous Remarks: — Shells ii^om the type lot, sent to 

 the National Museum and now under the label of variety wardii 

 of Lea, and numbered 134,639, are now in the writer's collection 

 through the kindness of the collector, B. F. Bush. However, it is 

 the opinion of the writer that this form may not deserve a name 

 since metanevra is subject to so many intergrades due to local con- 

 ditions. The above comparative description shows its departure 

 not far from type, besides the form is inconstant. 



Quadrula cylindrica (vSay). 



("Razor Handle,"" Cob Shell," "Rabbit's Foot," 



"Spectacle Case.") 



PI. XIX, Figs. 52 A and B. 



1816 — Unio cylindricus Say. Nich. Ency., II, PI. IV, fig. 3. 

 1819 — Unio naviformis Lamarck, An. Sans., Vert. VI, p. 75. 

 1900b — Quadrula cylindrica (Say) Simpson, Proc. U. S. Nat. Mus., 

 XXII, p. 773. 



ANIMAL CHARACTERS. 



Nutritive Structures: — Branchial opening moderately 

 large with brownish yellow tentacles; anal finely papillose; supra- 

 anal briefly connected to anal by mantle edge; gills very long and 

 narrow, outer more narrow anteriorly, inner laminae free from 

 visceral mass; palpi long, narrow connected one-third of their 

 length antero-dorsad; color of soft parts peculiar, foot with orange 

 back-ground striped in black, visceral mass uniorange, mantles 

 with black pigment especially along the margins at siphonal 

 openings. 



Reproductive Structures: — Only sterile marsupia found, 

 these with normal structures of Quadrula. Glochidia unknown. 



SHELL CHARACTERS. 



External Structures: — vShell rectangular-elongate, length 

 three times the height, dorsal posterior ridge, long, high, slightly 

 costated; wide behind, abruptly rounded before; post-umbonal 

 ridge high, hummocky and pustulate; umbones low, somewhat 

 sharp pointed, incurved, sculptured by corrugated ridges breaking 

 into tubercles out on disk; epidermis dark straw painted (as 



