382 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 53. 



The type, Cat. No. 322291, U.S.N.M., comes from Maldonado, 

 Uruguay. It measures — length, 83 mm.; height, 59 mm.; diam- 

 eter, 38 mm. It was donated to the United States Mational Museum 

 by Dr. F. Felippone, of Montevideo, Uruguay, in whose honor I take 

 pleasure in naming the species. 



In richness and warmth of coloring, regularity of form and outline 

 and in its appearance of exuberant health and prosperity this is one 

 of the handsomest of the Diplodons. Externally it mimics some of 

 the forms of Anodoniiies wymani and might pass for that shell if 

 mixed in with a series of that species. 



Its relationships point in two directions — namely, toward D. rvdus 

 Lea and D. paranensis Lea. Both of these species show the obsolete 

 radiating ribs noted in the description oi feUpponei. From D. rudus 

 it differs in outline, in not having a compressed posterior area and in 

 being nearly straight instead of sinuate along the hinge line, and espe- 

 cially in the character of the pseudocardinals which, in D. rudus, are 

 long and thin and placed parallel to the hinge line. From D. para- 

 nensis it can be distinguished at once by the elliptic outline, lack of the 

 inflated ventral margin and by the character of pseudocardinals. 



Another specimen of this same species is Cat. No. 180782, which 

 measures — length, 77 mm.; height, 54 mm.; diameter, 31 mm. It 

 comes from Arroyo Sarandi Grande, Uruguay, and was received from 

 Mr. S. Olea. It is an exact duplicate of the type in every detail 

 except size and state of preservation. The ratios of its length to 

 height and to diameter are almost exactly the same as those of the 

 type. This specimen has been in the collection since 1904 without 

 specific name. 



Since the above was written I have identified for D)^to^ Felippone 

 five specimens of this species. One of these (hi.-! No. 593) from 

 Arroyo Maciel, Florida, Uruguay, is, in some respects, superior to 

 the type, especially in size. It measures — length, 94 mm.; height, 

 68 mm.; diameter, 40 mm. His numbers 606, 609, 610, and 611 

 each include a single valve in a poor state of preservation. They 

 come from Rio Yi, Durazno, Uruguay. 



DIPLODON FORTIS. new species. 



Plate 52, figs. 1-4. 



Shell thick, heavy, and much swollen. Outline clongately sub- 

 quadrate, regularly rounded in front, prolonged into a blunt point 

 behind, resembling in general form many specimens of Uiiio tetralas- 

 mus Say. Posterior dorsal ridge full, higli, and rounded. A faint 

 rib traverses the posterior area from the beak to a point just above the 

 posterior angle. Ventral and dorsal margins nearly parallel. Sur- 

 face with indistinct concentric fine lines, the rest periods indicated 

 by dark lines. Anterior and middle portion with obscure radial 

 sculpture. Color chestnut brown, darker posteriorly. Beaks eroded. 



