M. Ussow’s Zoologico-Embryological Investigations. 317 
ridges from the beak to the ventral margin, separated by 
slightly narrower deep concave spaces; near the beak (for 
about half an inch) all the ribs set with strong blunt trans- 
verse tubercles, about their own thickness apart (about five 
in two lines), but on the adults the middle and lower ends of 
the ribs are marked only with irregular lines of growth, like 
the intervening hollows, except the seven or eight anterior 
ones, on which the large blunt tuberculation is continued to 
the ventral margin (about three in two lines). Length from 
anterior to posterior end 2 inches 3 lines; proportional width 
from beak to opposite margin 5°25; depth of one valve 53,45 ; 
hinge-line 55,5. 
This species is much larger, thicker, and stronger than the 
living or the other two Tertiary species, and is readily distin- 
guished by the tuberculation (except near the beak) being con- 
fined ; the anterior ribs having, the middle and posterior ones 
only slightly wrinkled by, lines of growth. The inner edge 
is strongly toothed by the projecting ends of the channels 
between the radiating ribs. Sometimes the two small most 
posterior ridges bear tubercles. 
This species was collected by Mr. Howitt from the beds of 
sandy marl at Jemmy’s Point, near the entrance of the Gipps- 
land lakes, containmg Struthiolaria and other forms which I 
have observed in the Pliocene Tertiaries of New Zealand, but 
not of any other locality in Victoria. I have great pleasure 
in naming so interesting a fossil after so excellent and zealous 
a geologist as Mr. Howitt has proved himself in the Gipps- 
land district. 
X L1.—Zoologico-Embryological Investigations. 
By M. Ussow. 
{Concluded from p. 221.] 
CEPHALOPODA (conclusion). 
To render clearer all the processes described by me, I think 
it will be useful to enumerate once more the principal facts of 
the embryonal development of the above-mentioned Cephalo- 
poda in their normal sequence. 
After the greater part of the protoplasm of the primitive 
ovicell, or the formative vitellus which surrounds as with an 
envelope the whole mass of the transparent fatty fluid (nutri- 
tive vitellus) has been converted, in the manner already de- 
scribed (see the process of segmentation), into a layer of flat 
