CHECKLIST OF THE AMPHIBIA OF MEXICO 97 



Species. — Approximately 400, about 25 American, of wliicli 9 are 

 Mexican. 



KEY TO MEXICAN SPECIES OF RANA 



1. A dorsolateral glandular fold 2 



No dorsolateral glandular fold 8 



2. Legs long; tibiotarsal articulation (heel) reaching tip or beyond the 



tip of snout 3 



Legs short, the heel reaching to a point between tympanum and snout 

 tip __ 5 



3. Heels overlap strongly (several millimeters) when legs are folded 4 



Heels touch when legs are folded; a fold behind tympanum; skin with- 

 out ridges but with small, rounded, pearly-tipped pustules and tuber- 

 cles of varying sizes, making skin rough to touch; subarticular tuber- 

 cles moderately large, rather elongate, compressed; toes swollen at 

 tips, fully webbed; 120 mm pustulosa (p. 98) 



4. Glandular fold narrow; skin without distinct pustules, smooth to touch; 



toes widened into flattened terminal disks, and fully webbed; no 

 vocal sac; heel far beyond tip of snout; 91 mm._ sierramadrensis (p. 98) 

 Glandular fold thick, widened; numerous longitudinal ridges or elon- 

 gate pustules between folds; toes pointed, not dilated at tips, almost 

 completely webbed; two external vocal sacs in males, behind jaw 

 angles; (composite); 115 mm pipiens (p. 98) 



5. Heel to between eye and tip of snout 6 



Heel not reaching beyond eye 7 



6. Heel to between eye and nostril; tympanum large, about % or more of eye 



diameter; posttympanic fold obsolete; 2 small internal vocal sacs in male, 

 the openings in floor of mouth very small; toes swollen at tips into 

 small disks, almost fully webbed; skin shagreen above, with minute hard 

 pearly-tipped tubercles; canthus distinct, sharp; 125 mm. 



palmipes (p. 98) 

 Heel to nostril or between nostril and snout tip; skin fold on upper lip hght 

 colored; fore part of head smooth; remainder of dorsum and sides with 

 small rounded papillae; first finger longer than second; canthus indis- 

 tinct; Baja Cahfornia; 114 mm aurora draytoni (p. 99) 



7. Feet and hands rather small or moderate; subarticular tubercles minute; 



tips of toes minutely swollen; heel to tympanum or between tympanum 

 and eye <'; first finger longer than second; longitudinal pustules or ridges 

 between dorsolateral glandular folds; sides strongly studded \nth smaU 

 equal-sized tubercles; belly unicolor usually; 116 mm. 



montezumae Baird (p. 99) 

 Feet and hands large, first and second fingers equal or first shorter; tips 

 of toes perceptibly larger than montezumae, the subarticular tubercles 

 small; no conspicuous tubercles between dorsolateral folds; heel to eye; 

 belly reticulated, grayish or grayish black and yellow; 152 mm. 



megapoda (p. 100) 



8. Diameter of tympanum two-fifths to one-half diameter of eye; tarsal fold 



present, distinct or indistinct; toes swollen into small disks; heels to or 

 near to tip of snout; no outer metatarsal tubercle; no vocal sac or external 

 vesicles behind ear; 78 mm tarahumarae (p. 100) 



<• In making this measurement the specimen must be straightened. If the back is slightly humped, the 

 heel will reach farther forward and the variation will seem greater than actually obtains. 



