292 BARON NOPCSA ON THE SUPPOSED [June 6, 
This highly remarkable coincidence suggests the probability that 
the bone in question represents an asymmetrical but nevertheless 
unpaired organ. 
So far as I am aware there is no known reptile, living or 
extinct, in which the clavicle is bifurcated at one end. Moreover, 
in most terrestrial and aquatic reptiles, when clavicles are present 
there is also an interclavicle, which has never been found in 
Sauropoda. It must also be remembered that these large 
herbivorous Dinosaurs were probably descended from the carni- 
vorous Theropoda, which are always destitute of a clavicular 
arch, 
Text-fig. 49. 
Os penis of European Otter. 
[ am therefore of opinion that the problematical bone of 
Diplodocus in question cannot be a clavicle, and it is necessary 
to consider Hatcher’s alternative suggestion that it is an os 
penis. 
The fact that existing birds and reptiles are destitute of an os 
penis does not necessarily imply that gigantic reptiles like 
Diplodocus similarly lacked the bone. Among Mammalia it is 
well known that the element occurs only sporadically, being 
present, for instance, in the Anthropoid Apes and absent in Man. 
Among the living reptiles we know two types of genital organs. 
The Squamata show what may be called a bifid penis, while the 
Crocodilia and Chelonia have the penis simple exteriorly, with a 
corpus fibrosum and frequently even a glans penis well developed. 
