BULLA. 327 



specialization in form of those retained, it parallels the Scaphand- 

 ridce ; but the specialization has been in a different direction corre- 

 sponding to the wide difference in food of the two groups, — Scaph- 

 andridoi being carnivorous, whilst 5t///tc?ce are exclusively herbivor- 

 ous. The absence of epipodial lobes is also different from Scaphan- 

 dridce, the animal in Bxdlidcc having the external form of that of 

 Toniatinidce. From both of these families the Bidlida' differ more- 

 over, in shell characters, form and non-calcification of the gizzard 

 plates, etc. 



The AkeridcG nre a much lower stock of Tectibraucbs than 

 Bullidce, retaining the primitive multi-dentate radula, and the 

 epipodial lobes, and having a thin, fragile unicolored shell. 



A few unicolored species, none of them known anatomically, are 

 referred to the genus Bulla ; but as a rule the shells are well distin- 

 guished from all other Tectibranehs by their characteristic mottled 

 coloration. 



But one genus is represented in the recent fauna. No extinct 

 groups are known to be referable to this family. 



Genus BULLA Linne, 1758. 



Bulla L., Syst. Nat. (x), p. 725.— Brug., Encycl. Meth. i, p. 368, 

 and of most modern authors. — Bullus Montf., Conch. Syst. ii, p. 330, 

 type B. ampula. — Bullea Blainv., in part, section B, Malacol., p. 

 478, and of Menke and Morch, not Bullma Lam. — Vesica Sw'Ains. 

 Malacol., p. 360.— iV^w-T, DaCosta Elem. of Conch., p. 174, 1776 

 (not binomial). — ConJ. Vayssiere, Rech. Zool. et Anat. sur les 

 Moll. Opisthobr. Ire pt. Tectibranches, p. 13 (anatomy of B. 

 striata). 



Shell oval or ovate, compactly involute, generally solid and with 

 a mottled color-pattern ; spire sunken, umbilicated. Aperture as 

 long as the shell, rising slightly above the vertex, its upper portion 

 narrow, expanded toward the base ; lip simple, flexuous ; columella 

 short and concave, with a crescentic white reflexed callus ; parietal 

 wall smooth, with a light parietal callus. Type B. ampulla L. 



Animal capable of complete retraction into the shell. Head-shield 

 rounded in front, produced behind in two rounded posterior pro- 

 cesses separated by a median sinus; eyes small, wide apart, about 

 half-way back on the shield. Epipodial lobes wanting. Foot large, 

 nearly as long as the shell, roundly subtruncate behind, wide and 

 blunt in front (pi. 43, figs. 7, 8, B. quoyi). 



