APRIL 4, 1912| 
necessary gangways, occupied an area of nearly two- 
fifths of an acre. ‘Lhe maximum quantity of steam pro- 
duced in any one hour was more than 800 lb. at atmo- 
spheric pressure, and while this is by far the greatest 
quantity ever produced by sun power, it must be pointed 
cut that Philadelphia is by no means an ideal situation 
for such a plant, for we had to wait weeks to get a 
nea-iy cloudless day, and then fortunately had three 
in succession. 800 lb. of steam per hour is equivalent 
to a boiler efficiency of 43 per cent. The plant was 
built at Philadelphia simply for the convenience of 
being close to the inventor’s house, offices, and labora- 
tory. In places like Egypt, Africa, Arizona, and 
California, I should expect to get about 25 per cent. 
more steam for the same collecting area. 
A. S. E. ACKERMANN. 
THE FLYING REPTILES OF THE CHALK 
PERIOD.* 
N the remarkable collection of fossil vertebrates 
obtained by the late Prof. O. C. Marsh for the 
Peabody Museum of Yale University, there are many 
NATURE 
128 
clearness with which his facts and conclusions are 
presented, and he displays commendable caution in 
his references to crushed and distorted specimens. 
The bones are so delicate that nearly all have col- 
lapsed by pressure in the laminated chalky rock, and 
it is therefore often difficult to determine precisely 
their original shape. 
The species of Pteranodon and its allies are the 
latest and most specialised flying reptiles, and so 
attain the greatest size. A nearly complete pair of 
wings mounted in the British Museum (Natural 
History) measures 18 ft. in span, and Dr. Eaton 
estimates that some specimens had a span of more 
than 22 ft. The adaptation of their bones to unusual 
mechanical needs is therefore of extreme interest. 
The well-known firm articulation of the scapula with 
a mass of fused thoracic vertebre, for the support 
of the large wings, is now described in detail, and 
Dr. Eaton thinks there were not more than three 
separate dorsal vertebrae between this fused mass and 
the equally rigid sacrum. The tail is very short and 
small, and the slender hind limbs must have supported 
the postero-internal borders of the wing-membranes. 
The elongated jaws 
of Pteranodon it- 
self are completely 
toothless, and Dr. 
Eaton_ observes 
that there is never 
an indication of 
vestigial tooth- 
sockets. The arti- 
culation for the 
mandible is 
obliquely __ ridged 
and grooved, so 
that the two 
branches would be 
thrust a little 
apart when the 
jaw opened, as in 
the pelican. It is 
therefore inferred 
that the animal 
was a fish-eater 
and had a small 
pouch below the 
Restoration of Pteranodon, Marsh ; from the left side. 
groups of which he only published preliminary notices. 
Among these the toothless Pterodactyls, which he was 
the first to discover in the chalk of Kansas, are 
specially deserving of attention. During the past ten 
years they have been studied in detail by Dr. George 
F. Eaton, who has now completed his researches and 
published a beautifully illustrated memoir, which will 
be welcomed by palzontologists. So. long ago -as 
1904 Dr. Eaton prepared for the St. Louis Exposition 
a model of the skeleton of Pteranodon, of which a 
copy was subsequently given to the British Museum 
(Natural History), where it is exhibited in the Gallery 
of Reptiles. In his new work he now reviews the 
whole of the material which forms the basis of this 
restoration (shown in the accompanying figure), and 
his concise descriptions are illustrated not only by 
admirable photographs of the fossils themselves, but 
also by explanatory sketches of several of the most 
important parts. 
Dr. Eaton is, indeed, to be congratulated on the 
1 “Osteology of Pteranodon.” By Dr. G. F. Eaton. Pp, 38+xxxi 
plates. Memoirs of the Connecticut Academy of Arts and Sciences. vol. ii. 
(New Haven, Connecticut : [Published under the auspices of the Yale 
University, 1910.) 
NO. 2214, VOL. 89] 
For convenience of representation the right limbs are omitted. 
| interest in the corresponding English fossils, 
mandible. 
In two species, 
though apparently 
not in a_ third, 
the supraoccipital crest is enormously extended, and 
would probably serve for the origin of very large 
temporal muscles giving great snapping power to the 
jaws. Even for such a purpose the crest appears to 
be sometimes too large, but Dr. Eaton concludes that 
it could scarcely be needed as a counterpoise to the 
long jaws, because ‘‘the form of the cervical vertebrz 
indicates a strong musculature of the upper part of 
the neck.” He alludes to ‘‘the general theory that 
growth along certain lines may be initiated through 
the exercise of one function, while further develop- 
ment is dependent upon another totally distinct 
function.” The crest may be an illustration of the 
so-called momentum in evolution. 
It will be remembered that many years ago the late 
Prof. H. G. Seeley devoted much attention to the 
fragmentary remains of these gigantic specialised 
Pterodactyls found in the Cambridge greensand, and 
attained great success in interpreting them. The new 
work on the better-preserved specimens of Pteranodon 
from the North American chalk will excite renewed 
and 
facilitate more exact studies of them. A. S. W. 
