218 MOLLUSCA. 
acute, of about ten nearly flat whorls separated by a well-marked 
suture. Aperture less than one-third the length of the shell, oblique, 
semi-lunar, with a depression at the lower angle (anteriorly) scarcely 
amounting to a notch ; outer lip thick, not reflexed, though apparently 
so when viewed in front, polished; pillar margin arcuate, with callus 
posteriorly, and also a considerable intrusion just above the rostral 
region, which, ending suddenly, is the principal cause of the apparent 
notch. 
Length of axis one-fourth of an inch; breadth one-tenth of an inch. 
Inhabits Clermont Tonnerre, Paumotu Islands. Couwthouy. 
The characters of this little shell are somewhat abnormal. Its size 
and sculpture would suggest Trwncatella ; its aperture is somewhat like 
the effuse form of Ewhma; the form of the aperture is also like Pyra- 
midella, with which I at first placed it, though it has no proper plaits, 
but merely an intrusion of callus with an adjacent sinus in place of 
them, and in this, is ike Monotigma. It agrees in all respects with 
Rissoa, except in the effuse base of the aperture. 
Figure 261, 261 a, front and lateral view of the shell, enlarged ; 
2614, aperture much enlarged; 261 c, natural size. 
ToRNATELLA BULLATA (Gould). 
Testa parva, ovata, tenuis, albida, epidermide stramineo fugacissimo 
induta, spiraliter sulcata, sulcts inearibus ad quinque ordinatim dis- 
positis in singulis anfractibus: spira prominula, turrita; anfractibus 
quinque tabulatis, ultimo magno, ventricoso, quindecim-sulcato, super- 
nis planulatis ; sutura canaliculata: apertura semilunaris ; columella 
uniplicata, planulata. 
Tornatella bullata, Goutp ; Proceed. Boston Soc. Nat. Hist., 11. 251. 
December 1847. 
SHELL small, thin, smooth, whitish, covered with a most delicate 
straw-coloured epidermis. The whole surface is marked with regu- 
larly arranged, deep, linear, revolving grooves, of which there are 
