34 NAIADES OF MISSOURI 



of post-dorsal ridge few, broad, shallow and faint; epidermis leathery 

 red to black, rarely yellowish or greenish. 



Internal Structures: — Cardinals double in both valves; 

 laterals single in right, double in left valve; umbonal cavities nar- 

 rowly deep; muscle scars well impressed; nacre marble white 

 with blue and old rose tints posteriorly; deep vein mark on antero- 

 extra pallial border. 

 Sex Length Height Diameter Localities. 



cf loi X 64 X 54mm (Mississippi R., La Grange, Mo.) 



9 112 X 74 X 46 " (Osage R., Monegaw Springs, Mo.) 



9 48 X 40 X 29 " (Mississippi R., Hannibal, Mo.) 



cf 33 X 28 X 20 " (Osage R., Osceola, Mo.) 



Juveniles of latter measurement very globose; epidermis 

 olivaceous with a reddish brown band in center parallel to growth 

 lines; post umbonal ridge rather prominent; one heavy undulation 

 at post base with two heavy furrows on either side. The very 

 greatly inflated beaks of adult shell is doubtless due to the globular 

 shell of the jtiveniles. 



Miscellaneous Remarks: — Amhlema peruviana (Lam) is 

 the Qviadrula plicata (Say) of authors according to the recent 

 decision of Mr. Bryant Walker who is making a special study 

 of original Lamarckian types. Mr. Walker states that Say's 

 type of plicata came from Lake Erie and is the form that Lea 

 describes as hippopaea and that peruviana is a form of the Ohio 

 shell commonly railed plicata but which is really the rariplicata 

 Deshayes. This species should perhaps be reduced to the sub- 

 species, " Amb. rariplicata peruviana (hsiTn); however, because 

 of its difference from rariplicata in the possession of full beak 

 and more globular juvenile shell it is left in specific rank. It is 

 found in typical form in the Mississippi north of the Missouri, 

 is scarce but rather typical in the Osage, but is not found at all 

 in the interior north of the Missouri, River. 



Amblema rariplicata (Deshayes) 

 ("Ohio Plicata," 'Few Ridge," "Big Blue Point.") 

 PL IX,— Fig. 20; PI. XV I, —Figs. 36A-D. 

 1830 — Unio rariplicata Deshayes, Enc. Meth; II, p. 578; An. Sans. 

 Vert., 2d. ed., VI, 1835, p. 533; 3d. ed., II, 1839, p. 667. 



animal characters. 

 Nutritive vStructures: — Branchial opening very long with 

 short yellowish papillae; anal slightly crenulate; supra-anal very 



