Marwick.—The Struthiolariidae. 171 
two weak cinguli below, fine spirals covering the whole surface. Later 
in life the shell is heavily calloused (C. parasitica is completely covered), the 
wing is more prominent, and the columella curved. This condition shows 
that a gerontic stage has been reached, 
ized and soon died out, while the ae 
Monalaria stock persisted. dire. 
The next еселі was а  Conchothyra marshalli Trechmann (juv.) ; 
: : А : Selwyn Rapids. Compare with Mona- 
shortening of the axial ribs into laria minor (Plate 11, figs. 5, 6, 7). 
tubercles, accompanied by evolution 
of the spiral sculpture along two different lines—(1) fine equal spiral lirae 
on à bicarinate body, (2) strong cords below a tubercled shoulder. 
e former retains the straight columella and is the typical Monalaria 
(in which the previous stage is here included generically); but in the 
latter, Struthiolarella, the columella becomes curved, and a considerable 
eallus forms in some species. 
In Struthiolaria s. str., which seems to date from the early Miocene 
or late Oligocene, there is a change in the outer lip, which om 
m an earlier common ancestor, slightly in advance of Monalaria. 
A study of the ontogeny of the Australian species might throw some light 
on this point. 
ж * * ж * * * 
An analysis of the published lists of New Zealand Tertiary Mollusca, 
with a view i 
pe 
liable to force all New Zealand Tertiary strata into one horizon. There 
is already a tendency in this direction, for several geologists have put the 
whole of the Oamaruian into the Miocene. | 
