i-^V 



62 NAIADES OF MISSOURI 



supra-anal region. This lack of mantle connection is a constant 

 character in this species, whereas this deciduity is inconstant among 

 other Quadrulae. The fact of its partial union of the inner laminae 

 of the inner gills with the visceral mass is also a departure from 

 the general characters of this genus and a step toward the modern 

 arrangement. In this latter character nobilis is somewhat like 

 Megalonaias heros. From the fact that females were found sterile 

 all through early and mid summer, it may be inferred that its 

 breeding season is very short and begins early in spring, or like, 

 heros begins late in the season. Later investigations may 

 relate this species more closely to Megalonaias for the physiolo- 

 gical reasons as well as for the morphological. 



Quadrula verrucosa Rafinesque. 



("Deer Horn," "Buck Horn.") 



PI. XIX, Figs. 30 A—D. 



1820 — Unio {Obliquaria) verrusoca Rafinesque, Ann. Gen. Phys. Brux. 

 1823 — Unio tuberculata Barnes, Am. Jl. Sci., VI, p. 125, PI. VII, figs., 



8a, 8b. 

 1899 — Tritogonia tuberculata Simpson, Pr. U. S. Nat. Mus., p. 608. 

 1912a — Quadrula tuberculata Ortmann, Ann. Car., Mus., p. 254. 



ANIMAL CHARACTERS. 



Nutritive Structures: — Branchial opening densely set 

 with arboreal papillae, anal crenulated, supra-anal smooth, very 

 large, slightly (even deciduously) connected to anal by mantle 

 edges; gills very long, comparatively narrow, inner broader, 

 inner lamina of inner gills connected to visceral mass except for 

 a short distance anteriorly; palpi very long, connected antero- 

 dorsad for a little more than half their length; color of soft parts, 

 mostly solid white, gills brown. 



SHELL CHARACTERS. 



External Structures : — Shell rather large, elongate, roughly 

 trapezoid; male shell shorter, more pointed posteriorly and 

 angled dorsad; female shell much longer, biangulated post-ventrad; 

 disk profusely tuberculated, the coarser tubercles located ventrad; 

 post-umbonal ridge prominent and nodulated; slopes of post- 

 dorsal ridge faintly costated, beaks rather small, apiculated, 

 sculptured with double-looped, zigzag markings that extend out 

 on the disk, epidermis chestnut brown to dark horn color. 



