Hullt-ria. | GASTROPODA. 533 



behind. Stomach containing 3 dumb-bell-shaped chitinous plates. 

 Radula having few longitudinal rows of teeth, formula 1 + 2+1 + 2+1 ; 

 the central tooth transverse, bar-shaped, with reflexed multidentate 

 cusp, a submedian denticle smaller : laterals 2 on each side, claw- 

 shaped, with numerous denticles. A cuspless plate lies outside of the 

 outer lateral. 



Shell wholly external, globose, oval, or oblong-cylindric, with um- 

 bilicated vertex (rarely covered) and sunken spire, mottled colour- 

 pattern, and smoothish surface ; aperture as high as the shell, rising 

 above the vertex, narrow above, dilated below ; columella simply 

 concave, with reflexed crescentic callus and no fold. 



The animals are herbivorous. 



Genus 1. BULLARIA, Rafinesque, 1815. 



Bullaria, Rafinesque, Anal. Nat., 1815, 142 ; new name for Bulla, Liniie. 

 Type : Bulla ampulla, L. Bulla, Linne, 1758, Syst. Nat., 725 ; not of 

 Linne, op. tit., 427, nor of Miiller, 1776. Bullus, Montfort, 1810. Bullea, 

 Blainville, 1825. Qondole, Latreille, 1825. Vesica, Swainson, 1840. 



Animal capable of complete retraction into the shell. Head- 

 shield rounded in front, produced behind in 2 rounded posterior 

 processes 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. Gizzard containing 3 subequal nearly similar 

 horny or chitinous plates, which are dumb-bell-shaped on the outer 

 surfaces, the inner or grinding surfaces being somewhat truncated,' 

 wedge-shaped, with flat tops. The side view shows a ledge (where 

 the muscles of the stomach-wall are attached) separating the outer 

 from the grinding face. Radula large, with dark chitinous teeth ; the 

 laterals not differentiated from the marginals ; central tooth like a 

 transverse bar, its reflexion with numerous denticles, the median one 

 smaller ; laterals claw-shaped, with about 6 long denticles ; outside 

 of the second lateral lies a small thin basal plate without cusps, the 

 remnant of a third lateral tooth. 



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

 a mottled colour-pattern ; spire sunken, umbilicated ; aperture as 

 high 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 callus. 



The species inhabit sandy mud-flats, the slimy banks of river- 

 mouths, and brackish places near the sea ; at low water some of them 

 conceal themselves in the mud and under seaweed, exuding large 

 quantities of mucus to maintain the moisture of their skin. 



Distribution. Warm and temperate seas. 



Fossil in the Cretaceous, Eocene, Oligocene, and Pleistocene. 



