USE OF CHARTS IN TEACHING VERTEBRATE PALEONTOLOGY 53 
line of the centrum. For amphiplatyan vertebrae the lines at 
the ends of the centrum are not altered, but for procoelous, 
opisthocoelous, and amphicoelous types the suitable curved 
dotted lines are to be used. It has been found useful to out- 
line the several elements composing the vertebrae with hachures 
as is shown in the illustration of foot structure (fig. 1). 
The importance of the rib articulation has long been recog- 
nized. No two animals with different rib articulations can be 
closely related. For this reason the facets on the vertebrae 
should be carefully noted. In the lateral view of the vertebra 
the small dotted circles permit the designation of all possible 
rib attachments. For a double, diapophysial attachment a 
cross should be placed in each of the two circles on the diapo- 
physis. Obviously the small half circles at the posterior end of 
the centrum are used to indicate intervertebral attachments. 
No doubt the guide charts as here presented are inadequate 
in many respects and not unlikely will they be found to contain 
certain errors. Other uses of the charts may suggest themselves 
and perhaps other forms may be added. The writer has tried 
forms for showing the structure of the pectoral and pelvic girdles 
and also a form for showing the evolution of the teeth. In both 
of these cases, however, the results were of doubtful benefit 
because of the complexity of fche charts. 
