MAMMALIA. 



445 



families to hold their own. Serious charges are brought 

 against the rats of being the carriers of various diseases, e. g., 

 of the bubonic plague. (Figs. 236-238.) 



FIG. 237. 



FIG. 237. The Fox Squirrel (Sciurus ludoricianus). Photographed by Folsom. 



FIG. 238. 



FIG. 238. Porcupine (Erethizon}. By Dr. J. W. Folsom. 



Questions on the figure. To what order of mammals does the 

 porcupine belong? What are its peculiarities of habit and structure? 



Order 7. Insectivora (insect-feeders). These are small 

 mammals with clawed digits, which feed on insects and other 



