564 



tudinal lines; spire prominent; apex obtuse; whorls three, rounded; 

 aperture narrowly ovate, anteriorly produced, outer lip acute, 

 grooved internally, inner lip posteriorly thin, reflected, adnate, 

 anteriorly twisted. 



Ceylon. Br. Sibbald. Mus. Cuming. 



Sub-genus Aplustrum. 



4. Bulla Thalassiarchi (pi. cxx. f. 4, 5, 6), Martini, 

 Chemn. x. t. 146, f. 1350, 1351. Aplustrum fasciatum, ScJium. 

 Bulla amplustre, Limi. Aplustra pulcliella. Swains. Bulla 

 aplustre, Lamarck, vol. vi. p. 35. 



B. testa ovata, subcylindrica, pellucida, nitida, fasciis albis et 

 rubicundis sen incarnatis ac lineis nigricantibus adnatis cincta ; 

 columeUse labio reflexo ; spira obtusa. 



Shell ovate, subcyhndrical, pellucid, sliining, encircled with 

 white and reddish or flesh-coloured bands, and adnate blackish 

 lines ; columellar lip reflexed ; spire obtuse. 



Mauritius ; in mud at the mouths of rivers,, Mus. Cuming. 



5. Bulla Gouldii fpl. cxx. f. 7), Coutlmj, Bost. Journ. 

 Nat. Hist. ii. p. 183, pi. 4. f. 6. 



B. testa parva, ovata, convoluta, fragili, alba, nitida, subopaca, 

 epidermide memljranacea olivacea tecta, transversim tenue striata ; 

 spira depressa, discoidea, imperforata, interdum prominula, an- 

 fractibus quatuor, superne rotundatis, suturis impressis ; apertura 

 supra angusta, versus basin dilatata ; columella arcuata, alba, 

 nitida, imperforata. 



Shell small, ovate, convoluted, fragile, white, shining, sub- 

 opake, covered with an olive membranous epidermis, transversely 

 finely striated ; spire depressed, discoid, imperforate, sometimes 

 rather prominent, whorls fom-, rounded above, sutures impressed ; 

 aperture narrow above, dilated towards the base ; columella arched, 

 wliite, shining, imperforate. 



Massachusetts Bay, U. S. 



6. Bulla debilis (pi. cxx. f. 8), Gould, SilHman's Journ. 

 xxxviii. 196. 



B. testa oblique ovata, parva, peUucida, cornea, inflafca, Isevi,, 

 subumbihcata ; spira distincta, plana, anfractibus quatuor; colu- 

 mella subrecta, antice abrupte truncata ; apertura ampla, antice 

 dilatata. 



