392 JR. S. Lull — Cranial Musculature in Dinosaurs. 



passive defense. Many of the injuries are such that none 

 other than a Ceratopsian could have inflicted them, and this, 

 together with the line mechanical development of the great 

 muscles, especially those in the wake of the supraorbital 

 horns, shows that, in spite of apparent unwieldiness, Tricera- 

 tops was an aggressive fighter when thoroughly aroused. In 

 the type skull of Dicer atops hatcheri Lull (1905) in the 

 United States National Museum, the so-called foraminia 

 through the anterior part of the squamosal bones almost 

 entirely obliterate the insertion of the complexus minor muscle 

 of the left side, and partially obliterate that on the right. 

 Enough, however, remains to indicate that the muscle depres- 

 sions were precisely as in Triceratops. This strengthens the 

 conviction which the writer has always had, that these perfora- 

 tions are entirely pathologic ; moreover, the wounds must in 

 large measure have disabled the animal and may ultimately 

 have caused its death, though it lingered on long enough for 

 the broken margins of the bone to heal, a matter of a few 

 weeks. 



Part II. Origin of the Crest. 



The crest, which is so characteristic of the Ceratopsia, has 

 its "parallel in the so-called casque of the chameleon skull. The 



Fig. 2. 

 Fig. 3. 



Chameleo vulgaris ; adapted from Parker. 

 Chameleo jJumilis ; " " " 



latter, however, while variably developed in different species 

 of chameleons, never reaches the extreme degree of perfection 

 which was attained by Trioeratops. 



