LAMPSILIS VENTRICOSA COHONGORONTA IN THE POTOMAC RIVER.
BY WILLIAM A. MARSHALL.
In 1912 Dr. A. E. Ortmann recorded[[2]] finding in the Potomac River a variety of Lampsilis ventricosa[[3]] to which he gave the name cohongoronta. His records were:
September 4, 1909. Potomac River, Hancock, Washington, Co., Md. (about two dozen).
May 9, 1911. South Branch, Potomac River, Southbranch, Hampshire Co., W. Va. (about a dozen).
August 16, 1911. Shenandoah River, Harper’s Ferry, Jefferson Co., W. Va. (a single male, below medium size).
May 6, 1912. South Branch, Potomac River, Romney, Hampshire Co., W. Va. (about a dozen).
Dr. Ortmann remarked “It is probable that this species will turn up elsewhere in the Potomac. The localities known at present are all to the west of the Blue Ridge Mountain, that is to say, within the Great Alleghany Valley and the Alleghany Mountains.”
Perhaps the above prediction has been realized in a specimen found at Great Falls, Md., by Mr. Manly D. Barber of Knoxville, Tennessee, in Sept. 1915. At that time Mr. Barber brought to the National Museum a basketful of naiades which he had collected the same day at Great Falls, about 18 miles above Washington. Among the shells, which were mostly dead ones, was a specimen of cohongoronta, dead, but in a fine state of preservation and with the periostracum nearly unblemished except for the usual erosion at the beaks. Its appearance indicated that it had been recently alive and that its home had been in the immediate vicinity of the place in which it was found. Had it been washed down from Harper’s Ferry, some 50 or more miles above Great Falls it probably would have shown ill effects from so long a journey.
When found the two valves were separated, but so accurately do they fit together that it is evident they belong to the same individual. The fact that the valves were separated and yet were found near each other is additional (though not conclusive) evidence that they had not been transported any great distance by currents. At any rate this is the first recorded finding of the species in the Potomac River so far south as Great Falls.
The specimen is rather a small one. It measures, length 71 mm.; height 47 mm.; diameter 28 mm. It is in the collection of the U. S. National Museum, catalogue number 273834.