142 THE NAIADES OF MISSOURI 



1900b — LampsHis ellipsijormis Simpson, Proc. U. S. Nat. Mus., XXTl, 

 P- 557- 



ANIMAL CHARACTERS. 



Nutritive Structures: — Branchial opening with numerous 

 yellowish papillae; anal very finely papillose; supra-anal small, 

 high, closely but distinctly connected to anal; gills large, pointed 

 even in the marsupial ones; inner laminae of inner gills connected 

 entirely to visceral mass; palpi sickle-s'haped; color of soft parts 

 the usual dirty white with posterior mantle edges blackened. 



Reproductive Structures: — Marsupium occupying posterior 

 half of outer gills, consisting of about twenty ovisacs separated by 

 thick septa, when gravid extending below the original edge of sterile 

 marsupium, tips pigmented with bluish, beaded spots; mantle 

 edge antero-ventrad to branchial opening with papillae terminating 

 in rather fine crenulations centrad-ventrad ; conglutinates and 

 glochidia unknown. 



External Structures: — Shell small, elliptical, dorsal and 

 ventral lines about the same curviture; post-umbonal ridge rather 

 rounded; beaks very low, usually eroded, even in the youngest 

 shells, thus sculpture not seen; epidermis brownish-yellow with 

 bright waved rays all over disk; no sculpturing on disk; shells 

 somewhat sexually dimorphic, the female being rather swollen 

 post-ventrad. 



Internal Structures. — Cardinals strong, upright; inter- 

 dentum large and thick ; laterals short, stout, very slightly curved ; 

 beak cavities shallow; nacre white, sometimes with slight pinkish 

 tinge and teeth rusty-red. 



Sex Length Height Diameter Locality 



cf 56 X 33 X 22.5mm (Gasconade R., Gascondy) 



cf 43 X 28 X 21.5mm (Osage R., Warsaw) 



9 41 X 25 X 17.5mm ( " "., Proctor) 



9 35 X 22 X 7.5mm (Niangua R., Hahatonka) 



Miscellaneous Remarks: — This little striped shell is common 

 throughout Central Missouri, but is never found anywhere in the 

 interior north of the Missouri River and is rare in the southern 

 drainage. Its shell may sometimes be taken for young N. liga- 

 mentina; however, the adult shells of these species are nothing alike. 

 The anatomy of both are very similar; however, the inner mantle 

 edge antero-ventrad to branchial opening is more specialized and 

 indicates a step in advance. Hundreds of females were examined 



