ACANTHOGLOSSATE AND BELOGLOSSATE TEETH. 
267 
The Steiiodoiitoplioroiis species, according to the character of the 
apices of the teeth or the modification they have undergone, may be 
divided into three chief groups, viz. : Acanthoglossa, Beloglossa 
and Echinoglossa. 
The Acanthoglossa (aKavda, a prickle ; yAwcra-a, tongue) possess 
spine-like or sickle-shaped teeth (as fig. o.Sd), a form which would 
seem more especially to characterize the carnivorous genera, but no 
species under our especial survey possesses a radula exclusively formed 
of this type of tooth, although Rhytidu and other tropical genera 
show characteristic examples ; this group is, however, enumerated 
here as some of our genera possess Acanthoglossate teeth in conjunc- 
tion with those of the Pycnoglossate type, and in such cases the 
Acanthic teeth always form the marginal series and generally tend 
to approach the median line at a more acute angle than the (quadrate 
teeth usually do. 
The teeth may be simply thorn-like or, by cleavage of the apex, 
form bispinose or trisi)inose teeth, the accentuation of this feature 
becoming more and more marked as the margin of the radula is 
approached. 
Proctonotlda’ amongst the Opisthobranchs and Bhjtlda zmowg 
the Pulmonates show characteri.stic exam})les of this type, almost 
identical in form and arrangement. 
The Beloglossa (fitXos, an arrow ; yAwcru-i/., tongue) or species 
with barbed teeth are confined in this country to the predatory genus 
Testacella, and would appear to be a special modification of the 
Acanthoglossate type, adapted to more securely retaining their hold 
upon the earthwonns upon which the Testacellw chiefly prey. 
