73 



careful to subjoin to the generic names that are liere adopted, ab- 

 breviations of the author's names, who formed them respectively, 

 or whose generic definitions I have followed. 



Type and Class MOLLUSCA GASTEROPODA. 



Patella amcena. — Shell oblong-oval, whitish reticulated with 

 reddish-brown, and sculptured with numerous minute concentric 

 wrinkles and close set radii ; margin entire j apex placed behind the 

 middle, and pointing backwards. 



Coast of New England States. 



Length of a small specimen, seven-twentieths, breadth one-fifth 

 of an inch. Breadth of a larger one three-tenths, nearly. My cabinet. 

 ^It may be readily distinguished in general by the beautiful 

 reticulated disposition of the rufous color, inclosing small irregularly 

 oval, white, or yellowish-white spots. They sometimes, however, 

 are of a uniform greenish or brownish color. Several specimens 

 of this species were communicated to me by Mr. Aaron Stone, who 

 found them on the coast of Maine. 



FissuRELLA alternata. — Shell oblong-ovate, moderately 

 thick, cinereous or dusky, with equal concentrated lines, crossed 

 by alternately larger and smaller radii, all which are equable or not 

 dilated in any part ; vertex placed nearer the smaller end ; perfora- 

 tion oblique, oblong and a little contracted in the middle ; within 

 white ; margin simply crenate ; apex with an indented transverse 

 line at the larger end of the perforation. 



Length four-fifths of an inch. Breadth three-fifths. Height 

 more than two-fifths. Inhabits the coast of the United States. 

 Cabinet of the Academy, and Philadelphia Museum. 



Bears a general resemblance in its sculpture to F. grse,ca, but the 

 radii are not dilated at the points where they are crossed by the 

 concentric lines. I have specimens from the coast of Maryland 

 that measure one inch and a half in length. 



Crepidula fornicata ? var. — Shell transversely wrinkled, 

 varying in convexity, with obsolete longitudinal, undulated, rufous 

 lines ; one side more oblique than the other ; apex excurved, a little 

 prominent, but not separated from the body of the shell, and gene- 

 rally united with the margin of the aperture ; aperture suboval ; 

 diaphragm a little concave, occupying at least half of the length, 

 edge generally declivate. 



