254 hylid.t.. 



the heels overlap, and the tibio-tarsal articulation 

 reaches the eye or between the eye and the nostril. 

 Besides, the vocal sac is larger, and the voice deeper, 

 whence the name barytonns, which has been given to 

 it by Heron-Royer. 



Fig. 94. 



Hind limbs of Hyla arborea, showing variations in the proportions 

 of the tibia and foot. The dotted line indicates the middle line 

 of the body. A. $, f. typiea, St. Malo. B. $, v. Savignyi, 

 Jerusalem, c. J 1 , v. meridionalis, Cannes. 



These structural differences are, however, far from 

 constant ; there are intermediate forms, as, for in- 

 stance, the var. molleri, which Bedriaga defines as a 

 H. meridionalis with the coloration of the typical form. 

 A male specimen from Ciudad Real may, I think, be 

 referred to it ; the heels slightly overlap, the tibia 

 measures 17 mm. and the foot 15, just as in a H. meri- 

 dionalis, but the coloration is that of the typical form, 

 and the specimen was identified as such by Bosca. A 

 female from Coimbra, received from Dr. de Beclriao;a 

 himself, agrees in the proportion of the limbs : tibia 

 22 mm., foot 20. 



A glance at the preceding tables of measurements 

 suffices to show that the difference in length between 

 tibia and foot, so considerable in the extremes, is 

 bridged over in such a manner as to render a precise 

 definition impossible. The same may be said of the 

 development of the vocal sac. We have therefore to 

 fall back upon the coloration for diagnosing the three 

 forms, and this is surely not enough to justify their 

 being treated as species, the more so as the var. 

 savignyi is itself a connecting link between the typical 



