1885.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 289 



Vol. Till, I¥o. 19. IVashins^ton, D. €. Au^. 6, 188«(. 



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going through the press aud a detailed description must be deferred. 

 The following notes, however, will indicate its exjternal characters: 



When living, the creature is of a uniform slaty blue, the under parts 

 bluish white, with a greenish tinge to the veil. The surface appears 

 boauiilully smooth and velvety without dorsal tubercles; just within 

 the slaty margin of the mantle is a single row of about (in all) one 

 hundred whitish elongated tubercles. When crawling, it is of an oval 

 shape about an inch long, and two tentacles extend forward beyond 

 the mantle margin, resembling the oculiferous ones of Vaginulus Jlori- 

 danus. ly spirits the surface is still smooth, but numerous circular 

 hardly-elevated domelets cover the back, each appearing to contain 

 one of the dorsal eyes described by Semper. The tentacles are entirely 

 retracted; a narrow veil, with lightly escalloped edge, precedes the 

 head; the muzzle is not prominent, is indented in the middle and 

 puckered at the edges. The foot is about one third wider than the 

 mantle at each side of it. There is no jaw. The penis resembles that 

 of Siphonaria in form and position. The animal exudes very little 

 mucus. It was found on rocks between tides associated with Chiton 

 piceus. Fifteen specimens were found at Knight's Key by Hemphill. 



Onchidiuni indolens of Couthouy (Kio) and 0. armadillo of Morch differ 

 from the above in coloring. The latter, described from St. Thomas, 

 has a very different dorsal surface. No others are known from East 

 America. It would seem as if the small northern species, possessing a 

 jaw like 0. horeale Dall and 0. celticum Cuvier, might appropriately be 

 separated from the aguathous tropical forms as a subgenus, for which 

 the name of Onchidella might be revived in a restricted sense. 



Family Corbiculid^. 



Sphaerium contractum Prime. 



Sphaerium contractiim Prime, Am. Corbicul., p. 48, fig.' 46, 1865. 

 Uahitat. — Brook near Enterprise, Lake Monroe, Florida, Dall ; Ala- 

 bama, Showalter. 



Pisidium abditum Haldeman. 



Pisidium ahditum Haldeman, Proc. Acad. Nat. Set. Phil., i, p. .53, 1841; Prime, 

 1. c, p. 68, fig. 72. 



Habitat — In Florida, Pensacola, Hemphill; river near Palatka, Dall ; 

 spring near Tampa, Stearns; North America in general, from New Eng- 

 land to Honduras, New .lersey to California, Prime. 



This species seemed abundant, and was the only one of the genus 

 observed by me in Florida. 



Washington, July 1, 1885. 

 Proc. Nat. Mus. 85 19 



