' THE NAIADES OF MISSOURI 17I 



smooth reddish-brown with bright green rays arranged all over 

 its shell. 



Interna:^ vStructurES: — Cardinals double in both valves, 

 laterals double in left, single in right; beak cavities rather shallow; 

 nacre white or light bluish. 



Sex Length Height Diameter Locality 



cT 45 X 22 X 15mm (Jack's Fork of Current R.) 



9 35 X 18 X lomm (White R., HoUister) 



9 34 X 16 X iimm (Black R., Williamsville) 



c? 22 X 12 X 7mm (Jack's Fork of Current R.) 



The last measurement is that of a young shell that shows a 

 beak sculpture of a profusely double-looped or corrugated ridges 

 the latest one being the strongest and running down quite low on 

 the disk. 



Miscellaneous Remarks: — For this State iris is strictly 

 a southern shell, being only found in the White and Black River 

 basins. Perhaps this pretty little shell is much more common 

 than supposed, since it is so liable to escape observation due to 

 its minuteness of size yet its bright green rays of uneroded shells 

 make it rather conscpiuous in clear shallow water. It has been 

 found to be bradytictic. 



Eurynia (Micromya) brevicula (Call). 



("Broken Rays," "Soul-of-Wit.") 



PL XXVII; Figs. 98 A~D. 



1887 — Unio breviculus Call, Pr. U. S. Nat. Mus., X, p. 499, pi. XXVIII; 



Tr. Ac. Sci. St. Louis, VII, (1895) p. 6, pi. XVI. 

 1900b — Lampsilis breviculus Simpson, Pr. U. S. Nat. Mus., XXII, 



P- 533- 



animal characters. 



Nutritive Characters: — Branchial opening densely papil- 

 lose; anal crenulated; supra-anal large, high, well separated from 

 anal with thick, spotted mantle edges; inner laminae of inner 

 gills not free from visceral mass; palpi rather large, connected by 

 their edges one fourth of their length antero-dorsad. 



Reproductive Structures: — Marsupium rather kidney- 

 shaped consisting of ten or fifteen ovisacs well separated, with 

 bluish ventral border and each ovisac presenting a beaded appear- 

 ance of black pigmented spots; in female mantle border antero- 

 ventrad to branchial opening with a flap-like structure bearing eight 



