90 THE NAIADES OF MISSOURI 



EUiptio dilatata (Rafinesque). 

 ("Lady Finger," "Spike," "Pistol Grip.") 

 PL XXI, Figs. 66 A and B. 

 1820 — Unto (EUiptio) dilatata Rafinesque Monog. of Bivalves of Ohio, 



Ann. Gen. Sci. Phys. Brux. 

 1823 — Unio gibbosus Barnes, Am. JI. Sci., VI, p. 262, pi. XI, fig. 12. 

 1838 — Unio arclior Lea, Tr. Am. Phil. Soc, VI, p. 10, pi. IV, fig. 10. 

 1912b — EUiptio g^ibbosiis (Barnes) Ortmann, An. Car. Mus., VIII, 

 p. 271. 



ANIMAL CHARACTERS. 



Nutritive Structures: — ^Branchial opening small with many 

 short, blackish papillae; anal with a single row of low papillae; 

 supra-anal separated from anal by short mantle connection; 

 gills long and narrow, inner laminae of inner gills free — in some 

 instances connected about one-fourth of the way anteriorly; 

 palpi short, wide, connected antero-dorsad about two-thirds of 

 their length; color of soft parts soiled grayish with area in front 

 of branchial opening yellowish, pericardianl region invariably 

 reddish brown. 



Reproductive Structures: — Only outer gills are marsupial, 

 marsupia moderately swollen in center when gravid, dark tan; 

 conglutinates narrowly lanceolate, always whitish; glochidia 

 medium size, spineless, hinge line slightly depressed, measure' 

 0.200 X o. 220mm. 



SHELL CHARACTERS. 



External Structures: — Shell elonga-te-ellipsoid, gibbose, 

 thick heavy, post-umbonal ridge rounded, inflated; disk smooth; 

 beaks flattened, coarsely sculptured with five or six wavy ridges 

 more pronounced behind; epidermis dark brown to horn or 

 yellowish. 



Internal Structures: — Cardinals rather low, double in 

 both valves; laterals double in left and inclines to double in right 

 valve; interdentum very long, cut away in right to receive left 

 post-cardinal; umbonal cavities rather shallow; however, deeper 

 in female shell; nacre mostly dark purple, varies from all shades 

 of purple to salmon and white. 



Sex Length Height Diameter Um. ra. Locality 



? 135 X 65 X 43.0 0.260 (Miss. R., Hannibal) 



cf 120 X 50 X 38.0 0.255 (Osage R., Osceola) 



9 42 X 20 X 9.5 0.255 ( " " " ) 



cf 39 X 18 X 9.5 0.250 (Niangua R., Hahatonka) 



