404 MARINE INVERTEBRATES 
The entire absence of such important organs as the heart and 
gills, together with the fact that they are undoubted mollusks, | 
would indicate that the Scaphopoda are very degenerate animals. 
The circulatory and respiratory system of mollusks is typically 
of a high order. 
A great many specimens of the Dentalide dredged in New 
England waters are dead shells, occupied by a worm which seals 
up the larger opening, leaving only a small aperture through 
which it protrudes its long white body. These must not mislead 
the collector into a vain search for a mantle and other molluscan 
characteristics of anatomy. 
Some of the larger species of Dentalium from deep-sea stations 
are four to five inches in length. 
