File:The tailless batrachians of Europe (Pl. XV) (8164127352).jpg

254 hylidti:.
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 barytonus, which has been given to
it by Heron-Royer.
Fig. 94.
Hind limbs of Hyla arbor ea, 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. $, 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 Bedriasra
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