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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 Nautilus 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 



