THE NAIADES OF MISSOURI 1 63 



brown horn-color, sometimes with yellowish narrow bands parallel 



to growth lines, rayless. 



Internal Structures: — Cardinals double in right, slightly 



so in left valve and arranged parallel with laterals; interdentum 



short; laterals single in right, double posteriorly in left valve; 



beak and branchial cavities very deep and large , basin - like ; 



nacre white with light rosy pink in branchial cavities, border light 



bluish. 



Sex Length Height Diameter Locality 



d^ 10 X 82 X 65mm (Mississippi R.,Hanibal) 



9 95 X 75 X 66mm ( " " " ) 



9 66 X 50 X 42mm ( " " La Grange) 



Miscellaneous Remarks: — Capax has the most inflated 

 shell of the Naiades, yet because of the fact that it is rayless and 

 has no sex dimorphism, nor furrowed beak sculpture, nor pure 

 white nacre of L. ventricosa it must be removed far from the latter 

 although its immensely inflated shell would superficially class it 

 near ventricosa. Its great inflation is not any greater, however, 

 than that of the relative inflation of the laevissinia shell in the last 

 stage of its parasitic life. Most of all, anatomical material kept 

 by the writer, shows no mantle flap {PL XXVI, fig. gj B) as seen 

 in L. ventricosa, nor as to be noted in any Lampsilis, and the mantle 

 edge antero-ventrad to the branchial opening is not even as much 

 specialized as in laevissinia, or alata; hence its place perhaps 

 should precede laevissinia, at least, but is placed last in the group- 

 ing under this genus on account of its most peculiarly inflated 

 shell which may show an advance over the other species that show 

 the other extreme in possessing a compressed shell in their adult 

 life. Capax is very rare shell for this State. It has a rather limited 

 geographical distribution over the whole country ; however, Simp- 

 son reports it as abundant locally, yet the writer's experience in 

 collecting it for in the Mississippi is that it is rare even there and 

 it was considered a stroke of good fortune to secure glochidially 

 gravid material showing proptera characters. 



Genus Carunculina Simpson. 

 (Type, Unio parvus Barnes.) 

 1898 — Carunculina Simpson (in Baker, p. 109, as section). 

 1900b — Carunculina Simpson. Proc. U. S. Nat. Mus., XXII, p. 563. 

 (as subgenus); 1912b, Ortmann, Car. Mas., VIII, p. 337 (as subgenus). 



Animal Characters: — Branchial opening small with rather 



