50 THE NAUTILUS. 



sculpturing, which, when further studied, may form a subsequent 

 note for THE NAUTILUS. 



NEW VARIETIES OF CREPLDTJLA RTJGOSA NUTT. FOUND ON NATICAAND 



ON NORRISIA. 



BY MRS. M. BURTON WILLIAMSON. 



In the July number of THE NAUTILUS, Dr. Wm. H. Dall de- 

 scribes a variety of Crepidula nivea C. B. Adams, from San Pedro, 

 California, and this reminds me of a variety found upon Natica that 

 has not, to my knowledge, been described. 



When I began collecting shells in San Pedro Bay some years ago, 

 I found a specimen of this variety and it was for years a puzzle to 

 me. Although only a dead, white shell, it would not classify with 

 specimens in any tray of Crepidulas. It did not look like an aber- 

 rant form, so I was loth to label it as such. It was a white, porcel- 

 lanous specimen, shaped like some Crepidula rugosa, but much 

 more pellucid-looking, but differed from Crepidula excavata Brod., 

 in being thicker and in not having either the remote apex or the 

 oblique growth of that form. It was also larger in size than any 

 Crepidula excavata I had seen. Some seven or eight years after 

 finding this dead specimen, two live ones, excepting that the animal 

 had recently been removed, were found in the bay. I immediately 

 recognized the white, granular form, and these specimens were 

 maculated with cht-stnut-colored spots, and as would be expected, 

 these live forms were thinner and more pellucid. I afterward found 

 this puzzling variety in situ on a piece of Natica, Lunatia Lewisii. 



If a specimen varies from the type sufficiently to be detected, 

 dead or alive, it merits a varietal name, and for my own convenience 

 I have labeled it on my cards. For the convenience of other 

 students this white porcellanous shell with its brown spots might be 

 labeled Crepidula rugosa Nutt. var. naticarum. 



There is another variety of Crepidula rugosa Nutt. found on 

 Norrisia norrisii Sby. This Norrisia is a smooth, reddish-brown 

 turban shell, whose habitat appears to be on kelp. The Crepidulas 

 found on these shells are of a light magenta-pink in the interior. 

 These slipper shells are usually much flatter than typical C. rugosa, 



