THE NAUTILUS. 117 



nine low radial ridges, starting from the beak, near which there are 

 some intercalary ridges which become obsolete about the middle of 

 the disk; both ends ot" the shell are destitute of radial sculpture for 

 about one-fourth the total length; there is no defined dorsal area, 

 lunula or escutcheon. Length of valve 48; length behind the beak 

 80; height 34; height of beak above the hinge-line 2.5; (double) 

 diameter 26 mm. The sparse radial sculpture in the middle of the 

 shell is almost exactly like that of P. Candida, except that in the 

 latter there are obscure nodosities on the ridges and no infercalaries, 

 while both ends have obsolete radial lines. In one specimen of P. 

 Candida there are eleven ridges. The sculpture of P. arata and 

 africana is quite different. The base of P. pacifica is gently arcu- 

 ate. The specimen is registered in the U. S. Nat. Mus. as No. 

 110,4.";6. It may be added that the granulation of the surface in 

 P. Candida is much less dense and conspicuous. 



THE SHOWALTES COLLECTION. 



BY HEUBERf H. SMITH. 



Every student of North American fresh-water shells is familiar 

 with the name of Dr. E. R. Showalter. He collected, probably, 

 three-fourths of the Alabama Pleuroceratidce described by Lea, and 

 not a few of the Unionidce ; many of Anthony's species came from 

 him, and he corresponded for years with Lewis, Hartman and other 

 eminent conchologists. Dr. Showalter resided at Uniontown, Perry 

 county, and afterwards at Point Clear, near Mobile, and he made 

 extended excursions to the Caliaba, Coosa and other rivers of the 

 Alabama system. His work, interrupted by the Civil War, was 

 taken up again about 1867, tliough not apparently with the same 

 enthusiasm. Until Aldrich took up the task, Showalter was almost 

 the only man in this rich field, and his specimens are scattered 

 througli all our collections. 



Few naturalists know ihat Dr. Showalter had a collection of his 

 own, and fewer still imagine that it is in existence. It had, in fact, 

 a narrow escape from destruction. After Dr. Sliowalter's death the 

 shells were stored for years under his house at Point Clear. Like 



