26 NAIADES OF MISSOURI 



undata rubiginosa (Lea) a name which this form might well bear 

 because of its closer relation with F. flava (Raf.) [ = F. rubiginosa 

 (Lea)]. After a prolonged correspondence among Messrs. Simpson, 

 Walker and Frierson this rather common and peculiar form was 

 left to the latter for naming; hence the MS. name herein given. 



Miscellaneous Remarks: — This intergrade is very near 

 the form, undata-irigona, and differs only in being more elongated, 

 less upright, more rounded, post-dorsal margin, more reddish 

 epidermis, lower beaks, and is a larger, heavier shell. Those of 

 this variety that are found in the Mo. Platte of North Mo. have the 

 most ponderous shell of any of the Fnsconaia — some reaching 

 a length of loomm while the average length of the species (F. 

 undata) for the Mississippi only average 6omm. This variety 

 seems to be more of a creek form of F. flava and the reason for this 

 form being larger in the Platte R., a smaller stream, than in the 

 Osage, the largest tributary of the Missouri in this State, may be 

 traced as a mere local effect since the shells of other species in the 

 Mo. Platte are found to be abnormally large. Like most of the 

 Unioninae this form has a peculiar habit of aborting its conglu- 

 tinates when taken from its natural bed. The author has been 

 able to pick out for study the little pink club-shaped conglu- 

 tinates from whole masses of other white leaf -shaped conglu- 

 tinates of Ouadrulae or Pleurobemae that would also be aborted 

 after being collected from the river and placed in a tub or aquarium. 

 The habits of this form are that of deep and rapid burrowers and 

 inhabitants of deep water and coarse gravelly bottom. It is found 

 to be gravid from May until September and sterile for the rest 

 of the year. A proposed publication by Mr. Frierson on these 

 puzzling southwestern forms of Fusconaia will, without doubt, 

 clear up the situation. 



Fusconaia flava (Rafinesque.) 



(Pigtoe," "Red vShell," "Red Nose," "Wabash Pigtoe.") 



PI. XV. Figs. 32 A—D. 



1820 — Unio flavtis Rafinesque, Monog. Bio. Shells of R. Ohio. 



1829 — Unio rubiginosa Lea, Tr. Am. Phil. Soc, III, p. 427. PI. VIII, 



fig. 10. 

 J898 — Quadrula rubiginosa Baker, Moll. Chicago. Pt. I. p. 77, PI. 

 XIX, fig. i; XX, fig. I. 



1912 — Fusconaia rubiginosa Ortmann, An. Car. Mus., VIII, pp. 241 



242, Text Fig. 4. 



