“Var. _solidus_. Very solid, wide, ashen; inside whitish, the posterior valve with 10, central valve 2‒3, anterior valve 12 slits. Length 72, breadth 40, divergence 130°. Carpenteria, near Sta. Barbara, Cal. This is scarcely more than an individual variation. The mantle (girdle) is normal. The sculpture is worn away except at the edge. It has evidently lived in a very exposed situation.” From this description and the figure which he gives of the valves it would seem that this is the same form as my specimens from the pholad holes. I fully agree with Dr. Pilsbry that it is hardly worthy of varietal rank. It is, however, too distinct in appearance to be labeled simply _Ischnochiton conspicuus_, Cpr., and I have therefore marked these specimens from the pholad holes _I. conspicuus_, Cpr., _form solida_, Cpr., using the term _form_ as advocated by Dr. Cockerell, “to designate variations plainly due to environment.”[1] 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.