/ 



94 



THE NAIADES OF MISSOURI 



igi2h—Uniomerus tetralasmus (Say) Ortmann, An. Car. Mus.. VIII, 

 pp. 272 and 273. 



/AV _J 



Fig. 4. Uniomeriis tetralasma (Say) 9- Diagram of a gravid individual 



from Lost Cr., Amity, showing animal characters in left valve. 



Coll. May 3, 1913. (%" nat. size.) 



ANIMAL CHARACTERS. 



Nutritive Structures: — Branchial opening large, set with 

 numerous papillae; anal finely crenulate on inner edge; 

 supra-anal large extending to dorsal line, closed from anal by a 

 moderate mantle connection; gills about the same width, inner 

 'onger, inner laminae free from visceral mass for whole length 

 except for a short distance anteriorly; palpi short and broad, 

 connected only for one-fourth of their length antero-dorsad ; 

 color of soft parts, for most parts, a dingy white with mantle edge 

 at siphonal openings blackish, gills brown. 



Reproductive Structures: — Marsupia only occupying 

 outer gills, when charged rather padiform, distended at center, 

 but not near the ventral edges, ovisacs simple, undivided; con- 

 glutinates also undivided, white, sole-shaped, with regular thin 

 transparent areas arranged cross-wise made by the thickening 

 of the septa at regular intervals; glochidia spatulate, very regular 

 in outline, hinge line short and straight, medium in size measuring 

 0.160 X 0.210 mm. 



