NAIADES OF MISSOURI 57 



heavy shell, that occurs in the Mississippi Valley, North of the 

 Ohio and also of the Missouri Rivers. The differences in this 

 upright, rounded shell from its parent are stated in 'the compara- 

 tive description. Since students of Naiades have pronounced it 

 a variety, if found in sufficient numbers, the author concurs by 

 naming it for its type locality, Lake Contrary, St. Joseph, Mo. 

 Wherever found in this lake, the bottom is a soft, marly mud, 

 and the situations are in rather deep water sheltered from wave 

 'action. The author has discovered a short period breeding season 

 for contraryensis. 



Quadrula nodulata Rafinesque. 



(•'Pimple Back," "Warty Back.") 



PI. XVII, Figs. 44 A and B. 



1820 — Obliquaria nodulata Rafinesque, Bivalves of River Ohio, Ann. 



Gen. Sci. Phys. Brux. 

 1834 — Unio pustiilatus Lea, Tr. Am. Phil. Soc, p. 79, PI. VII, fig. 9. 

 1834 — Unio nodulatus Say, Am. Conch., VI. 



Animal Characters: — Nutritive structures absolutely iden- 

 tical with those of Qtiad. pusfulosa (Lea). The glochidial characters 

 are the same, except a difference in size, the glochidium of nodulata 

 being the larger 0.230 x 0.290 mm. However, small differences 

 in size may not be considered good distinctions as it is the glochi- 

 dial Jornt that is to be taken into greater account. 



SHELL CHARACTERS. 



External Structures: — Shell medium in size, solid, sub- 

 orbicular, inflated, post-dorsal ridge projected; umbones very 

 full, high, incurved bearing three or four small corrugated, con- 

 centric ridges; post-umbonal ridge and central part of disk orna- 

 mented with two radial rows of small, erect pustules sometimes 

 terminating with half-tubercles at ventral margins; epidermis 

 light tan to dark horn. 



Internal Structures: — Identical with pnstulosa. 



cf 48 X 40 X 30 mm 0.200 (Miss. R., Hannibal, Mo.) 

 9 45 X 38 X 28.5 " 0.250 ( " " " " ) 



cf 32 X 28 X 23 " 0.210 ( " " " " ) 



Shell of juvenile subglobose, post-umbonal ridge prominent, 

 post-dorsal ridge short, high; tubercles few in two rows — one on 

 post-ridge — no radial furrow between; beaks very full, sculptured 



