Chase. | ; 98 (July 20, 
below 43; forty-five transverse rows between nape and origin of tail, and 
thirty-six rows between front of humerus and vent. 
The interfrontonasal is transversely diamond-shaped, and has no exter- 
nal plates at its lateral margins. The frontonasals have considerable 
mutual contact. There are two postnasals; the anterior (and only) 
canthal descends to the labials, taking the place of the loreal, and there is 
one large preocular. A postmental follows the symphyseal, and then one 
pair of infralabials in contact. Two pairs follow, the anterior interrupted 
by one, the second by two, scales. The auricular opening is nearly as 
long as the fissure of the eye. The appressed limbs are separated by the 
space of four ventral cross-rows, or the length of the longest digit of the 
manus. The tail is of moderate length. 
Color of upper surface and sides, brown, the latter a little darker, and 
bounded above by a narrow black line. A somewhat irregular row of 
small black spots down the median dorsal line. Below yellowish olive, 
the scales of the abdomen with black borders, those of the gular and 
thoracic regions with black centres. 
Total length, M. .148; length to auricular meatus, .012; to axilla, .028 ; 
to vent, .061. 
From the summit of the Pico Blanco (elevation 11,500 feet) in the East- 
ern Cordillera of Costa Rica; W. M. Gabb. 
This species I provisionally identified with the G. fulous of Bocourt, 
which has been found in Guatemala. The two species are probably nearly 
allied, but present a difference in the cephalic scutellation, which is of 
generic value. 
Further Illustrations of Central Force. 
By Priny EaruE CHAssE, LL.D., 
PROFESSOR OF PHILOSOPHY IN HAVERFORD COLLEGE. 
(Read before the American Philosophical Society, July 20th, 1877.) 
The establishment of centres of oscillation and harmonic nodes, in an 
elastic medium, is a necessary consequence of the principle that ‘‘a sys- 
tem of bodies in motion must be regarded mechanically as a system 
of forces or powers which is a perfect representation of all the single 
powers of which the system is compounded, and this, too, at whatever 
time or times the component powers may have been introduced into the 
system.’’ * 
But since it is often more difficult to grasp truths which are presented 
under new aspects, than those which are clothed in familiar garbs, it may 
be well to glance at some of the most obvious tendencies to nodal action, 
which result from simple gravitating fall towards a centre. The exami- 
PETC. EOC PAs Ae mes Lis lll, 
