MYRIAGLOSSATE AND DICflOGLOSSATE TEETH. 
271 
This peculiar dentition is in this country restricted to the 
PUmorhes, but has been shorvn to be also possessed by their possible 
progenitors, the so-called Pki/sa’ of Australia, the representatives of 
which, although now restricted to the Southern Hemisphere, had 
1) robably in former times a much more extended range. 
The IMyriaglo.ssa (/Lirptov, numberless ; yAwo-o-a, tongue) have more 
simply shaped and uniform teeth than many of the other Eurydonto- 
2) horous groups, and are characterized by the possession of a well- 
defined, though slender, mid-tooth, with a trifid reflection flanked by 
' ■ ' 
Fig. 542. — Transv'erse row of teeth from the odontophore of Helix pyginepa Drap. (highly 
magnified), Cambridge, prepared by Prof. Gwatkin. 
numerous closely set bicuspidate and obscurel}" tricu.spidate teeth of 
a practically uniform and usually simple hooked character ; the 
formula for JMlr pygmoca, a representative of this group, may be 
expressed .is : 
The Dichoglossa double ; yAwo-o-a, tongue) are represented 
by the genera IlyaUnla, Llnmx, etc., and are distingui.shed by 
possessing tricuspid median teeth, with variously cu.sped quadrate 
teeth on the central and pleural areas of the radula, the marginal series 
l)eing formed by teeth of the Acanthoglossate or Echinoglossate type. 
:->5 
Fig. 543. — Transverse row of teeth from the odontophore of Hyalinia nitidula (Drap.), highly 
magnified, prepared by Mr. J. W. Neville. 
The numerals appended to the figures of the teeth indicate their position in the transverse row. 
HydUma nitidula may be taken as typical for this section, and the 
peculiarities exhibited by its odontophore may be formulated as 
+ 4 + ^ + V + 35—2,485. 
This group may be looked upon as a link between the Aculeate and 
Quadrate teeth, as it combines Ijoth forms on the same membrane, 
and would thus seem to markedly indicate the omnivorous character 
of the species or groups possessing it. In this group certain genera 
will fall which further investigation may probably demonstrate to 
lie more suitably classified under other heads. 
