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motor organ usually called ‘‘ fleshy funnel ’’ in the modern nautilus, 
as has been explained above. 
It is useless to discuss the terms ‘‘ ventral”’ and ‘‘ dorsal.’’ There 
can be no debate on their application, unless it is based upon new 
anatomical information. The fact is obvious, so far as now known, 
that in Maudilus pompilius, and all other Nautiloids, the outer side 
of the whorl is ventral and the inner side is dorsal. Whenever, 
even in straight shells, Orthoceras, etc., the lines of growth can be 
seen, the ventral side is indicated by the ‘‘ hyponomic sinus,’’ and 
in nautilian or coiled shells it is invariably on the outer side. 
The term ‘‘ depressed ’’ is used for the flattening of the whorls, 
which affects the abdomen and dorsum and acts at right angles to 
the transverse diameter of the coil; ‘‘ compressed ’’ for the similar 
effect on the sides, which acts in the plane of the transverse diame- 
ters and at right angles to the plane of coiling. When the sides, 
lateral zone, or faces are inclined inwardly towards the umbilici, the 
term ‘‘divergent’’ is applied, and when they incline outwardly 
towards the abdomen the term ‘‘ convergent ’’ has been used. 
The adoption of these terms has been found to give clearer ideas 
of the development and true importance to the different characters 
of the volutions. The term ‘‘sides’’ is used in a general way, and 
distinguishes the whole of the lateral aspect of the whorl at any 
stage. The ‘‘lateral zones’’ and lateral faces, etc., as will be seen 
in the descriptions, are developed as modifications out of the sides 
of the young and immature whorls. The outer angles occurring on 
either side in the young or in the biangular forms are in the text 
named ‘lateral angles,’’ being really on the sides of the whorl and 
distinct from the angles arising later in the life of the individual, 
and later in the evolution of the group. The junction of the ‘¢ lat- 
eral faces’’ and abdomen are the ‘‘ abdominal angles,’’ and those 
of the ‘‘lateral faces’? and inner faces of the mature whorls 
are called the ‘‘umbilical shoulders,’’ and the inner surfaces 
are the ‘“‘umbilical zones.’’ All of these parts are developed in 
succession and in various combinations, from a round or elliptical 
form of whorl, having the vertical or ventro-dorsal diameter longer 
than the transverse, both in the individual and in the evolution of 
the group. 
The venter is the area between the outer angles, whether they be 
the ‘‘lateral’’ or ‘‘abdominal’’ angles, on the outer part of the 
whorl, and the ‘‘dorsum’’ is the corresponding part on the inner 
