coe 
NATURE 
[Mov. 3, 1881 
with gold as such, it is combined with the whole group AuCl,, a 
radicle that is doubtless far more chlorous than chlorine itself, 
If any were inclined to doubt the truth of this view, they 
should write the formula CINH, under NaAuCl,, when they 
would perceive that the radicle AuCl, corresponded to NH,, 
ammonium, the basylous properties of which no one doubted 
nowadays. 
In ammonium we have the basylous energies of four hydro- 
gen atoms concentrated by the inert nitrogen, and the result was 
a powerfully basylous radicle;,in AuCl, we have the chlorous 
energies of four chlorine atoms giving a powerfully chlorous 
radicle, 
Among other examples of the kind the Professor cited : 
K,AsF, with nonovalent atom, 
K,PtC), 
K,SiF 
O1(OH); 
KSbF¢ 
K,Fetk's 
K,Mgbr, 
a K,CuCly 
KMgC}, with tetravalent atoms. 
And he concluded his address by drawing attention to the condi- 
tions that affect the atomic value of an element, which he said 
were, firstly, the nature of the combining atoms; there was a 
limit to the number of atoms of one kind that can combine with 
a given element, but if the element combined at the same time 
with one or more atoms of a different character, this limit might 
be passed ; and secondly, the temperature, a sufficient rice of 
temperature being always accompanied by a diminution of atomic 
value. He thought it of great importance that these points 
should be considered by those who had artificially limited their 
horizon. The properties of many of the atoms in complex sub- 
stances having been in great measure concealed from view by the 
practice of giving specific names, such as the word ‘‘ molecular,” 
he thought it would be much better to say at once that we are 
ignorant of the constitution of these bodies than to resort to such 
names, 
with octovalent atoms. 
with heptavalent atoms, 
with hexavalent atoms, 
JURASSIC BIRDS AND THEIR ALLIES! 
BOUT twenty years ago two fossil animals of great interest 
were found in the Jithographic slates of Bavaria. One was 
the skeleton of Archeopteryx, now in the British Museum, and 
the other was the Com/sognathus y reserved in the Royal Museum 
at Munich. A single feather, to which the name Archaeopteryx 
was first applied by Von Meyer, had previously been discovered 
at the same locality. More recently another skeleton has been 
brought to light in the same beds, and is now in the Museum 
of Berlin. These three specimens of Archaeopteryx are the 
only remains of this genus known, while of Compsognathus 
the original skeleton is, up to the present time, the only 
representative. 
When these two animals were first discovered they were 
both considered to be reptiles by Wagner, who described 
Compsognathus, and this view has been held by various authors 
down to the present time. The best authorities, however, now 
agree with Owen that Archeopteryx is a bird, and that Compso- 
gnathus, as Gegenbaur and Huxley have shown, is a Dinosaurian 
reptile, 
Having been engaged for several years in the investigation of 
American Mesozoic birds, it became important for me to study 
the Furopean forms, and I have recently examined with some 
care the three known specimens of Arche@opteryx. I have also 
studied in the Continental museums various fossil reptiles, in- 
cluding Compsognathus, which promised to throw light on the 
early forms of birds. 
During my investigation of Archeofteryx I observed several 
characters of importance not previously determined, and I have 
thought it might be appropriate to present them here. The more 
important of these characters are as follows :— 
1, The presence of true teeth, in position, in the skull. 
2. Vertebre biconcave. 
3. A well-ossified broad sternum, 
4. Three digits only in the manus, all with claws. 
5. Pelvic bones separate. 
6. The distal end of fibula in front of tibia. 
* Read by Prof. O. C. Marsh before Section D,'British Association, at 
York, September 2, 188x, Communicated by the Author. 
7. Metatarsals separate, or imperfectly united. 
These characters, taken in connection with the free metacar- 
pals and long tail, previously described, show clearly that we 
have in Archeopteryx a most remarkable form, which, if a bird, 
as I believe, is certainly the most reptilian of birds. 
If now we examine these various characters in detail, their 
importance will be apparent. 
The teeth actually in position in the skull appear to be in the 
the premaxillary, as they are below or in front of the nasal 
aperture, The form of the teeth, both crown and root, is very 
similar to the teeth of Hesperornis, The fact that some teeth 
are scattered about near the jaw would suggest that they were 
implanted in a groove, No teeth are known from the lower 
jaw, but they were probably present. 
The presacral vertebree are all, or nearly all, biconcave, re- 
sembling those of /chthyornis in general form, but without the 
large lateral foramina. There appear to be twenty-one pre- 
sacral vertebra, and the same, or nearly the same, number of 
caudals, The sacral vertebree are fewer in number than in any 
known bird, those united together not exceeding five,fand 
probably less. 
The scapular arch strongly resembles that-of modern birds. 
The articulation of the scapula and caracoid, and the Jatter with 
the sternum is characteristic; and the furculum is distinctly 
avian, The sternum is a single broad plate, well ossified. It 
probably supported a keel, but this is not exposed in the known 
specimens, 
In the wing itself the main interest centres in the manus and 
its free metacarpals. In form and position these three bones 
are just what may be seen in some young birds of to-day. This 
is an important point, as it has been claimed that the hand of 
Archeopleryx is not at all avian, but reptilian. The bones of 
the reptile are indeed there, but they have already received the 
stamp of the bird. 
One of the most interesting points determined during. my 
investigation of Archeopteryx was the separate condition of the 
pelvic bones. In all other known adult birds, recent and extinct, 
the three pelvic elements—ilium, ischium, and pubis, are firmly 
anchylosed. In young birds these bones are separate, and in all 
known Dinosaurian reptiles they are also distinct. 
In birds the fibula is usually incomplete below, but it may be 
co-ossified with the side of the tibia. In the typical Dinosaurs, 
Zguanodon, for example, the fibula at its distal end stands in front 
of the tibia, and this is exactly its position in Archeopieryx, an 
interesting point not before seen in birds. 
‘The metatarsal bones of Archeopteryx show, on the outer face 
at least, deep grooves between the three elements, which imply 
that the latter are distinct, or unite late together. The free 
metacarpal and separate pelvic bones would also suggest distinct 
metatarsals, although they naturally would be placed closely 
together, so as to appear connate. 
Among other points of interest in Archeopteryx may be men- 
tioned the brain-cast, which shows that the brain, although com- 
paratively small, was like that of a bird, and not that of a 
Dinosaurian reptile. It resembles in form the brain-cast of 
Laopteryx, an American Jurassic bird, which I have recently 
described. The brain of both these birds appears to have been 
of a somewhat higher grade than that of Hesferornis, but this 
may have been due to the fact that the latter was ‘an aquatic 
form, while the Jurassic species were land birds, 
As the Dinosauria are now generally considered the nearest 
allies to birds, it was interesting to find in those investigated 
many points of resemblance to the latter class. Compsognathus, 
for example, shows in its extremities a striking similarity to 
Archaeopteryx. Thethree clawed digits of the manus correspond 
closely with those of that genus; although the bones are of 
different proportions. The hind feet also have essentially the 
same structure in both, The vertebra, however, and the pelvic 
bones of Compsognathus differ materially from those of Archeo- 
pteryx, and the two forms are in reality widely separated. 
While examining the Compsognathus skeleton, I detected in the 
abdominal cavity the remains of a small reptile which had not 
been previously observed. The size and position of this in- 
closed skeleton would imply that it was a feetus; but it may 
possibly have been the young of the same species, or an allied 
form, that had been swallowed. No similar instance is known 
among the Dinosaurs. é 
A point of resemblance of some importance between birds 
and Dinosuurs is the clavicle. All birds have those bones, but 
they have been considered wanting in Dinosaurs. Two speci- 
