NAIADES OF MISSOURI 33 



before maturity ("aborted") if disturbed. According to recent 

 studies of Dr. Ortmann and Mr. Frierson Amblema Rafinesque 

 should siipplant all previous names for this genus because Amb. 

 costata Raf. is without doubt Unio undulatus Barnes; hence the 

 following nomenclature: 



(i) — Amblema plicata (Say) 1817 = L^ plicatus Say. = L' . hip- 

 popea hea = Quadrula plicata hippopaea Simpson. 



(2) — Amblema plicata costata (Raf) i82o=L^. tmdulatus 

 Barnes 1S2 ;^=Quadrula undulata Simpson. 



(3) — Amblema peruviana (Lamarck) iSig = Ouadrtila plicata 

 Simpson. 



Note that because of the Law of Priority the local form 

 (plicata vSay) from Lake Erie must be considered unfortunately 

 as the main species, although other than taxonomic reasons would 

 not justify the recognition. 



Amblema peruviana (Lamarck) 



("Three Ridge," "Big Blue Point"). 



PL XVI,— Figs 35A and B. 



1 8 19 — Unio peruviana Lamarck, An. Sans. Vert., VI, p. 71., Deshayes, 

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



1900b — Quadrula plicata (Say) Simpson, Pr. U. S. Nat. Mus., XII, 

 p. 767. 



Animal Characters: — wSince this species is simply an Amb. 

 rariplicata (Des.) with very full, high beaks and with identical 

 soft parts, except a small difference of form due to a more elongated 

 shell with deeper umbonal cavities, we would refer our readers 

 to the description of these characters for rariplicata. Gravid 

 marsupia have the same structure. Glochidia of peruviana 

 are found to be semicircular, spineless, medium size, about as 

 long as high (0.200 x 0.210 mm.) 



SHELL CHARACTERS. 



External vStructures: — Shell elongate-quadrate with ven- 

 tral edge rather straight, post-dorsal portion bowed, heavy and 

 greatly inflated anteriorly, rather compressed posteriorly; beaks 

 high, full, incurved, well placed forward, sculpture consisting of 

 concentric lines forming two loops at base of post-umbonal ridge; 

 undulations four to five, coarse, oblique from ventral margin to 

 umbonal region across post-umbonal ridge; costae on slopes 



