48 FieLp CoLumBiAN MusgeEuM—GEovocy, VOL. II. 
/ 
lage bone like the precoracoid get entirely on the outside and seal in 
a membrane or dermal bone? I would sooner believe that the 
so-called clavicles are really precoracoids, and for this belief their 
position on the visceral side of all three cartilage bones, the scapula, 
episternum and coracoid, would lend some support. Inno case, how- 
ever, can I believe it probable that this cartilage represents the pre- 
coracoid. 
The same argument will apply in its entirety to the assumption 
that the ventral ramus of the scapula is in reality the precoracoid. 
In no specimen has it ever been found as a distinct ossification. It 
grows peripherally, enclosing the clavicles on their outer side. The 
elongated clavicles unite ‘by suture with the scapula in the Notho- 
sauria without the intervention of any precoracoid process. By the 
reduction of the clavicles and the extension of the acromial process in 
these animals we would get the Plesiosaurian girdle. Is it necessary 
to insert a distinct ossificatory element in this development? 
It may be added that Koken believes the precoracoid to be fused 
with the coracoid. 
I cannot, therefore, believe that the precoracoid is represented 
by any ossification in the plesiosaurian clavicular girdle. Nor do | 
believe there is any genetic relationship between the ventral ramus 
of the Plesiosaurs and that of the Chelonian scapula. If there is, is 
it not strange that in the one case the branch should lie ventrad to 
the clavicle and in the,other dorsad? I am well aware that in thus 
concurring in the views held by Seeley, Andrews, Koken, Baur and 
others, there are pertinent arguments on the other side given by 
Hulke, and especially Fiirbringer. * 
Petvic GirpLeE.—The fwvdzs varies but little from the usual form. 
It is a broad, flattened plate of bone, thinned throughout, except at 
the symphysial and acetabular articulations. It is, in general, quad- 
rilateral in shape, with the anterior inner angle broadly rounded, and 
the acetabular angle truncated. The posterior and outer borders are 
both markedly concave, and of about equal length. The anterior 
border is more nearly straight and irregular. The inner border is 
thickened on the posterior third or half, gradually becoming thinner 
anteriorly. The obliquely truncated sutural surface is much rough- 
ened. The two bones, when united, must have made an angle with 
each other of about one hundred and twenty-five degrees. I do not 
think that there was much cartilage between, the two, or that it 
extended back to the ischial symphysis, though it may. Anteriorly 
Jena. Zeitschr. 1900, p. 332. 
