vv^- 



50 NAIADES OF MISSOURI 



Miscellaneous Remarks: — Typically this species is a small 

 shell, very upright with beaks protruding extremely anteriorly 

 and with irregularly arranged pustules over its disk. In this 

 latter character it is separated from Q. nodulata with which it 

 is often confused; then too nodulata is not so rotund. Pustulosa 

 is more typically a southern shell while its variety, schooler a ftensis, 

 is more of a northern and western form. Its favorite home is clear 

 water and rather swift streams and is associated with Q. sphae- 

 rica, refulgens, mortoni, etc., — all of which are not found in Missouri; 

 on the other hand its northern relative (schoolcraftensis) is more 

 of a lover of mud bottom and sluggish current. It is strange that 

 this species is not found in South Missouri where its ecological 

 conditions are most favorable; however, it is not at all common 

 anywhere in the great South-west. It is occasionally found in 

 Central Missouri but mostly in varietal forms. The Mississippi 

 River is the only locality for anything like its type. It should 

 be a species of wide distribution since its host distributor is the 

 common crappie (P. annularis). 



Quadrula pustulosa schoolcraftensis (Lea). 

 ("Warty-Back," "Pimple-Back.") 

 PL XVII. Figs. 42 A—D. 



1834 — Ufiio schoolcraftensis Lea, Tr. Am. Phil. Soc, V., p. ,37, pi. Ill, 

 fig- 9- 



ANIMAL CHARACTERS. 



Nutritive Structures: — Branchial opening large, low, with 

 short arboreal papillae; anal obscurely crenulated; supra-anal 

 closely connected to anal but not deciduous; gills tilted at an 

 abrupt angle, inner laminae of inner gills entirely free from visceral 

 mass; palpi unusually long, somewhat curved; except brownish 

 gills and palps the soft parts are dull whitish or tan. 



Reproductive vStructures: — All four gills marsupial, septa 

 crowded, ventral edges pointed and distended slightly in center 

 when gravid; conglutinates white with thin, transparent spots 

 arranged transversely in rows; glochidia same in form as the 

 parent species, but a little larger (0.235 ^ 0.320). 



SHELL CHARACTERS. 



External vStructures: — Shell large, subquadrate, ventral mar- 

 gin gently curved, moderately inflated, thick, heavy; posterior 



