3 
A second undescribed species, represented by a skull and skeleton, is 
referred to the genus Lambeomurus . 
Another undescribed species, represented by a splendidly preserved 
skull (Oat. No. 8633), is here referred to Tetmgonosaurus. This skull is 
much larger than the types of either Tetmgonosaurus praeceps Parks or T. 
erectofrons Parks (16), and the hood is much higher, but the similar 
development of the premaxilbe and nasals suggests that it may best be 
placed in that genus. The larger size and more strongly developed hood 
could hardly be regarded as due to age development, for the open sutures 
seem to indicate that this head represents a less mature animal than either 
of those described by Parks. 
Conclusions. Scarcity of juvenile specimens is a disadvantage in a 
study of this kind. Some of the skulls under examination have the sutures 
open or the bones disarticulated, showing that the animals were not old, but 
few very young animals have been reported. The paucity of the remains 
of young dinosaurs in the delta deposits of the Belly River and Edmonton 
formations of Alberta and the abundance of such remains in the Mongolian 
desert deposits seem to suggest strongly that the eggs were deposited and 
the young reared on the upland and that only the older animals inhabited 
the swamps. 
Certain generic characters that seem to be dependable have been 
worked out and four of the genera that have been proposed for the Belly 
River forms appear to be justified, as will be shown later. 
Nopesa's theory (11) that the hooded hadrosaurs are the males and 
the flat-headed forms the females of the same species cannot be enter- 
tained, since the whole make-up of the skulls is different in the two forms. 
The enclosed narial passage with its complicated winding and trapping, the 
backward development and modification of the premaxillary and nasal 
bones, the great shortening of the skull, and the lengthening of the forearm 
among the Lambeosaurinae suggest different feeding habits from those of 
the flat-headed forms. These differences are too great to be included in the 
same subfamily, much less in the same species. Moreover, according to 
Nopcsa’s theory the males and females are, in some cases, not found at the 
same horizon and during the whole of Lance time only females existed, for 
none but flat-headed forms have been reported from rocks of this age 
although they have been collected over a very wide area. In the Edmonton 
formation, along Red Deer river, Alberta, the writer observed that from 
Drumheller upstream to the northern edge of township 31 the Hadrosau- 
rinae predominate, whereas north of this point their place is taken by 
members of the Lambeosaurinae. 
Professor Romer, in his Vertebrate Palaeontology, suggests that there 
may have been openings in the hood through which the animal could 
breathe, enabling him to remain submerged except for the top of the hood. 
The writer regards the openings in the hood as only lack of development 
or ossification of the bones. 
The hood is variable within the genus, but its development is not 
regarded as a sexual character. The trapping of air in the elongated narial 
passages and subsidiary air pockets in the hood was probably an aid to 
feeding under water. 
