564. 



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

 aperture narrowly ovate, anteriorly produced, outer Hp acute, 

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

 anteriorly twisted. 



Ceylon. Dr. Siblald. Mus. Cuming. 



Sub-genus Aplustrum. 



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

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

 Bulla amplustre, Linn. Aplustra pulchella, Swains. Bulla 

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



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

 rubicundis seu incarnatis ac lineis nigricantibus adnatis cincta ; 

 cohunellge labio retlexo ; spira obtusa. 



Shell ovate, subcylmdrical, pellucid, shining, 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 (pi. cxx. f. 7), Couthoy, Bost. Journ. 

 Nat. Hist. ii. p. 182, pi. 4. f. 6. 



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

 epidermide membranacea 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 four, 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, Silliman's Journ. 

 xxxviii. 196 k 



B. testa oblique ovata, parva, pellucida, cornea, inflata, lsevi, 

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

 mella subrecta, antice abrupte truncata ; apertura ampla, antice 

 dilatata. 



