1915.] Allen, Review of the South American Sciuride. 161 
Explanation of Text Figures 1-12. 
All figures one fourth nat. size. 
Figures 1-12 are to show relative size, and the relative length of the tail to the 
total length. Figures 13-16 are to show the number and position of the mamme. 
Fig. 1. Microsciurus similis similis (Nelson). No. 32497, Am. Mus., o ad.> 
Gallera, Western Andes, Colombia. 
Fig. 2. Leptosciurus pucheranit pucheranii (Fitzinger). No. 34621, Am. Mus., 
o ad., Fusugasug4, Eastern Andes, Colombia. 
Fig. 3. Leptosciurus ignitus ignitus (Gray). . No. 16560, Am. Mus., @ ad., 
Inca Mines, Peru. | 
Fig. 4. Notosciurus rhoadsi Allen. Type. No. 12725, Mus. Acad. Nat. Sci. 
Philadelphia.  juv., Paguma Forest, Chunchi, Ecuador. (See also Fig. 17.) 
Fig. 5. Mesosciurus hoffmanni hoffmanni (Peters). No. 18089, Am. Mus., 
o ad., Mount Irazt, Costa Rica. | 
Fig. 6. Mesosciurus gerrardi versicolor (Thomas). No. 34166, Am. Mus., 
o ad., Barbacoas, Colombia. 
Fig. 7. Guerlinguetus estuans estuans (Linné). No. 36492, Am. Mus., & ad., 
Bonasica, Essequibo River, British Guiana. 
Fig. 8. Guerlinguetus ingrami (Thomas). No. 36487, Am. Mus., o ad., 
Alambary, Sao Paulo, Brazil. 
Fig. 9. Hadrosciurus flammifer (Thomas). No. 16946, Am. Mus., o ad., 
Suapure, Venezuela. 
Fig. 10. Urosciurus tricolor (Poeppig). No. 19762, Field Museum, < ad., 
Yurimaguas, Peru. 
Fig. 11. Urosciurus duida (Allen). Type. No. 36153, Am. Mus., 9 ad., Rio 
Cunucunumé, base of Mt. Duida, Venezuela. 
Fig. 12. Simosciurus stramineus stramineus (Eydoux and Souleyet). No. 9014, 
U.S. Nat. Mus., & ad., Guayaquil, Ecuador. 
Fig. 13. Leptosciurus ignitus irroratus (Gray). Same specimen as Fig. 3. 
Fig. 14. Mesosciurus gerrardi morulus (Bangs). No. 170991, U.S. Nat. Mus., 
2 ad., Rio Indio, Canal Zone, Panama. 
Fig. 15. Guerlinguetus estuans quelchii (Thomas). No. 20036, Field Museum, 
9 ad., Serra da Lua (near Boa Vista), Brazil. 
Fig. 16. Urosciurus tricolor (Poeppig). Same specimen as figure 10. 
Ratio of tail length to the total length. 
Text Figures 1-12, pp. 162-164. 
The length of the tail vertebra, relative to the total length of the animal, 
varies greatly in different groups of tree squirrels, probably in relation to 
their habits, being developed in proportion to their exclusiveness as tree 
dwellers. The North American chickarees (Tamiasciwrus) and the Andean 
pygmy squirrels have the shortest tails of all the American species. Little 
