FAMILY ACERIDjE — BULLA. 15 



This species, which was first detected and described by Col. Totten of the U. S. Engineers 

 on the coast of Rhode-Island, and subsequently along the shores of Massachusetts, has also 

 been observed on our own coast. Those obtained by Dr. Jay near Rye, at low water on the 

 surface of the mud, are much larger than the Rhode-Island specimens, with which, through 

 the kindness of Col. Totten, I have been enabled to compare them. Mr. I. Cozzens has 

 obtained them from Staten island, below Quarantine ground, in seven or eight feet water ; 

 and Dr. Stillman, by dredging in the East river above Corlaer's hook. These latter were 

 olive-green, and covered with a rust-colored epidermis. When a number of these specimens 

 are kept in a close vial, they communicate a deep olive-green color to the water. 



Dr. Gould has thought proper to refer the solitaria of Say to this species. 



Bulla gouldii. 



PLATE V. FIG. 101. 



Bulla gouldii. Couthouy, Bost. Jour. Nat. Hist. Vol. 2, p. 181, pi. 4, fig. 6. 

 B. id. Gould, Invertebrata of Mass. p. 163, fig. 94. 



Description. Shell thin and brittle, small, ovate, convolute ; of four convolutions, rounded 

 at their upper edges, and having their sutures well defined, the last whorl with numerous fine 

 transverse stria;. Spire depressed, discoidal, sometimes slightly mammillated : incremental 

 striae very indistinct ; lower extremity rather narrower than the upper. Aperture narrow 

 above, and abruptly dilated towards the base by the arcuated inner margin, which is a little 

 thickened, white and polished. No umbilicus. 



Color. Shining dead white, with a yellowish epidermis. 



Length, 0"3. Diameter, 0"1. 



This species was first described by Mr. Couthouy, from specimens obtained from the 

 stomachs of fishes ; and was subsequently dredged by Col. Totten, in Provincetown harbor, 

 Mass. It will probably be found on our coast. Distinguished from insculpta by its fiat sum- 

 mit, displaying all the whorls. 



Bulla obstricta. 



PLATE V. FIG. 102. Magnified. 



Bulla obstricta. Gould, Am. Jour. So. Vol. 39, p. 196. 



B. id. Gocld, Invertebrata of Mass. p. 167, fig. 96. 



Description. Shell oval, cylindrical, rather solid, small. Whorls five, the last nearly in- 

 volving all the others, pressed in or obstricted at the middle, dilated beneath, and forming a 

 fold at the umbilical region. Spire obtuse, rising above the junction of the lip to about one- 

 fifth the length of the shell : upper whorls suddenly smaller. Suture deep, apparently double 

 in old specimens ; or, rather, a narrow and deep line revolving on the shoulder of each whorl 



