47 
1. 1. 1. 1. 1containing 19—22 series of teeth, Its length 0.32, breadth 
0 12 mm. Median tooth broad, with a slight middle incision of 
its edge, carrying 4—6 conical denticles on each side of it, the in- 
nermost and outermost ones smallest. Lateral tooth narrow, with 
a strong bent cusp. Marginal tooth broad, with 2 strong cusps, 
separated by a deep incision; no denticles on the external teeth. 
Gizzard armed with 4 hyaline chitinous crest-like bodies, com- 
posed of about 8 thick triangular pieces attached to a common 
basal plate. 
Locality: North Island, Cape Brett, the coast, among large Co- 
rallinae (St. 2), several sps., adult as well as young ones. 
Remarks. The features stated above, chiefly of the external hab¬ 
itus, are already sufficient to establish the systematical position of 
this interesting . little mollusc in the close vicinity of the genus 
Runcina belonging to the Tectibranchiate Opisthobranchia. With 
this genus it shares the general organization, absence of shell, 
position of anus, armature of stomach, and so on. At the same 
time, however, important differences are striking, above all the 
place and arrangement of the gilis and the structure of the radula 
(in Runcina and lldica having the formula 1.1.1.), characters justi- 
fying the creation of a new genus for the reception of the new 
species. Though the genus Runcinella thus occupies a position 
apart from the other genera of fam. Runcinidae it is the most con- 
venient to retain it within this same family, which, as far as hi- 
therto known, constitutes a well defined group of the Cephalaspidea. 
Anatomy. 
(Text-figs. 7—9.) 
Alimentary canal. In the muscular pharynx which is fixed 
to the body wall by means of muscle cords, a pair of thin mem- 
braneous jaws are lodged. The structure of these jaws is similar 
to that of the jaws in Runcina described by Vayssiére (1883, 
pi. 1, fig. 7), thus showing their surface closely beset with small 
rhomboidal corpuscles, each with a central denticle. A pair of tu- 
bular salivary giands debouch at the sides of the oesophagus. This 
soon opens into the very muscular gizzard. On the left side of 
the debouching point a short diverticle, like the one described 
by Colosi (1915) in Runcina calaritana, is inserted. It has the 
