NAIADES OF MISSOURI 65 



Sex Length Height Diameter Locality 



39nim (Miss. R., Hannibal ) 



36 " (Meramec R., Fern Glen ) 



25 " (Osage R., Proctor) 



30 " ( " " Greenwell Ford) 



6.5mm ( " " Osceola) 



Juvenile shell with three nodulous expansions on post umbonal 

 ridge, deep furrows between nodules; ligament bright pea green; 

 epidermis straw-color; slopes of dorsal ridge slightly ribbed; 

 beaks high upon dorsal line; posterior peculiarly roundly lipped 

 for the branchial opening. 



Miscellaneous Remarks: — The shell characters of metanevra, 

 typical of the whole genus, are highly emphasized. The enormous 

 supra-anal opening and yellow mantle border at the siphonal 

 opening are characteristic of its soft-parts. This species is well 

 represented in Central Missouri and in the Des Moines and Miss- 

 issippi, but is seldom found in North or South Missouri. The 

 writer has only found it in the Grand River of North Missouri 

 and while he himself has not found it in South Missouri, yet Mr. 

 Walker has it in his collection from Black River, Popular Bluff, 

 Missouri. Simpson (1900b p. 774) reports it for general distri- 

 bution throughout the Mississippi drainage area except its southern 

 portion, extending to the Tennessee and Arkansas rivers. Its 

 favorite habitat is sandy or gravelly shoals and, as its shell responds 

 to its surroundings, the general form of shell may vary so much 

 as to make it appear as a different species, or sub-species. Its 

 breeding season is found to be tachytictic. 



Quadrula metanevra wardii (Lea). 



(" Monkeyface.") 



Not Figured. 



1861 — Unio wardii Lea. Pr. Ac. N. Sci. Phila., V, p. 372; Jl. A. C. N. 

 Sci. Phila., V., p. 187, PI. XXIV, fig. 257. 



Animal Characters: — Identical, with those of its parent 

 species. 



SHELL CHARACTERS. 



External Characters: — Shell more elongated than its 

 species, comparatively smooth, heavier, more solid, post-umbonal 

 ridge with an expansion just before reaching basal line; otherwise 



