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 RIVER.* 
BY N. M. GRIER. 
I. On the Anatomy of Lampsilis higginsti Lea. 
Ortmann (1) is inclined to suspect that this species is merely 
a local form of ZL. 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 Aigginsii, obtained while 
in the service of the United States Bureau of Fisheries, con- 
vinces me of the conformity of higginsit 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 higginsi 
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. 
