80 THE NAUTILUS. 



fine specimens from the original localities that I will exchange 

 with museums and collectors for specimens or publications new 

 to my collections. 



NOTES ON THE NAIAD FAUNA OF THE UPPER MISSISSIPPI BIVER.* 



BY N. M. GRIER. 



I. On the Anatomy of Lampsilis higginsii Lea. 



Ortmann (1) is inclined to suspect that this species is merely 

 a local form of L. orbiculata Hildreth, the form of very large 

 rivers with muddy bottom, rather than the northern representa- 

 tive of that species, which some consider to be distinctly south- 

 ern. Examination of the soft parts of higginsii, obtained while 

 in the service of the United States Bureau of Fisheries, con- 

 vinces me of the conformity of higginsii with descriptive mater- 

 ial given for the genus Lampsilis by Simpson (3), and by Ort- 

 mann for L. orbiculata (2). 



The most important point of resemblance between these two 

 species is the common possession of a mantle flap greatly re- 

 sembling that in L. ventricosa, and which obtains its greatest 

 development in the female. As such a structure in higginsii 

 seems to have been overlooked, detailed description of it fol- 

 lows. The papillae on the posterior border of the mantle ob- 

 tain the greater development, those situated anteriorly being 

 quite stunted when present. At the beginning of the posterior 

 half of the mantle edge, the latter thickens to form a grooved 

 flap which shortly attains a width three times that of the ad- 

 jacent portions of the mantle edge, but which narrows down 

 above the anal opening to a width equal to that of the anterior 

 edge of the mantle. The greatest thickness is obtained at a 



* Published by permission of the United States Commissioner of Fisheries. 



1. Ortmann, A. R., "Notes upon the Families and Genera of Najades". 

 Annals of Carnegie Museum, Vol. VIII, 1912, p. 353. 



2. Ibid., "Monograph of the Najades of Pennsylvania, Part III". Me- 

 moirs Carnegie Museum, Vol. VIII, No. 1, 1919, p. 324. 



3. Simpson, C. T., " Descriptive Catalogue of the Naiades ". B. Walker, 

 Detroit, pp. 77-78. 



