PELONAIA. 27 



tliird, contain the apertnros. Tlic two polygons arc whccl-likc, 

 being radiated with six spokes from a centre, which is the sessile 

 aperture. Proceeding from and perpendicular to eacli of the dark 

 lines are lu'ight straw-colored fibres, extending toward the cen- 

 tres of the polygons, but not reaching them. Length, half an 

 inch. 



Dredged in forty fathoms, on a muddy bottom, off Long Island, 

 Grand Manan. One specimen only was found, which was adher- 

 ing to a dead valve of Pectcn Magellaiiicus. (^Sti/iipson.) 



Genus PELONAIA, Forbes and Goodsir. 1840. 

 Test cylindrical ; orifices terminal, four-cleft, on two small, ap- 

 proximated, papillose eminences ; mantle adherent to the test ; no 

 tentacles. Ovaries two, symmetrical. 



This genus, in its cylindrical body and terminal orifices, resem- 

 bles Siphiuicidus among the Echinoderms. They have relations 

 also with the Annulosa in the transverse plaits of the respiratory 

 sac, and in being bilateral. One of their most strikirg peculiari- 

 ties is the perfect union of the test and the mantle. The Pe- 

 lonaicE live buried in mud, quite unattached to any other body, 

 and are extremely apathetic animals, presenting scarcely any a|> 

 pcarance of motion. 



Pelonaia arenifera. 



Pelonaia airnifim, SxiMrsox, Proc. Bost. Soc N. II. iv. 49 (1851) ; Clieck Lists, 2 (18G0). 



The body is elongated, clavate, of a brownish color, and covered 

 with grains of sand ; the apertures are placed on two small, white, 

 mammilliform protuberances at the smaller extremity. It inhaljits 

 deep water ; the specimens were obtained from eighteen fathoms, 

 about ten miles cast of the Boston Lighthouse. {Stimpsoti.) 



