BULLEANA. MOLLUSCA- BULLA. 167 



by having two distinct tentacula, Deshayes, a much later authority, 

 says it is perfectly well ascertained that the animals accord with each 

 other most accurately. 



BULLI NA may at least be regarded as a sub-genus of BULLA, to 

 which this species and the next will belong. At the same time, its 

 shape and the fold on the columella would seem to approximate it to 

 VOLVARIA, where Mr. Say originally placed it. 



BULLA OBSTRI'CTA. 



Shell oval-cylindrical, white, nearly smooth, spire somewhat 

 elevated^ last whorl nearly as long as the shell, and slightly girt- 

 ed at the middle ; a fold on the pillar. 



FIGURE 96. 

 State Coll., No. 113. Soc. Cab., No. 2389. 



Bulla obstri'cta, GOULD ; Silliman'g Journ., xxxviii. 196. 



Shell small, cylindrical, with each extremity rounded, semi- 

 transparent, opaque white, or pale horn-color ; whorls five, the 

 last nearly involving the others, somewhat girt in at the middle, 

 nearly smooth, covered with a light-yellowish epidermis ; spire 

 obtuse, rising above the junction of the lip to about one fifth the 

 length of the shell ; suture deep, apparently double in old speci- 

 mens, or rather, a narrow and deep line revolving on the shoulder 

 of each whorl, near the suture, forms a sort of channel ; aperture 

 very narrow behind, widening before ; outer lip sharp, entire, join- 

 ing the preceding whorl by a gradual approach, and then turning 

 down the inner border in the form of a thick, slightly attached plate 

 of enamel ; from the front, as it turns back, it becomes thicker and 

 rounded, and at the umbilical region it enters the shell and forms 

 a conspicuous fold. Length T \ inch, breadth ? 4 T inch. 



Found on Chelsea Beach by myself, at Provincetown by Col- 

 onel Totten, at New Bedford by Prof. Adams, and is not unfre- 

 quently taken from fishes. 



The same remarks which were made under the preceding spe- 

 cies, as to its generic place, apply to this species. 



This shell closely resembles the figures, and agrees in general with 

 the description, of Bulla ollusa, of Montagu ; but in neither of them is 

 any fold at the base of the pillar noted, and our shell has a more ele- 



