No. I.] THE SKULL IN THE MOSASAURID^. 5 



Huxley), = paroccipital process of the exoccipital. The " squa- 

 mosal " is really the quaratojugal. 



In a later paper, published in June, 1871,^ we find some notes 

 about the quadrate bone. Professor Marsh commits the same 

 error as Professor Cope, describing the inner side of the quad- 

 rate as the outer, and vice versa. The pterygoid bones are 

 stated to be separated in Edestosaurus dispar, Marsh, except, 

 perhaps, at their anterior inner margin. To this I have to 

 state that they are separated completely, as in all Mosasauroids. 



The premaxillary of Edestosaurus velox is said to be united 

 with the maxillaries, anteriorly, at least, by suture. There are 

 also short notes about the basioccipital in Clidastes Wymani 

 and CI. pumilus. 



In April, 1872, Professor Marsh published a paper : Discovery 

 of the Dermal Scutes of Mosasauroid Reptiles, Am. Journ. Sci., 

 Vol. Ill, April, 1872. 



The so-called scutes are the bones of the sclerotic ring. The 

 Mosasauridae have no ossified dermal scutes, but the scutes are 

 very much like those of the Varanidae, as I have seen in the 

 original specimen, described by Professor Snow,^ preserved in 

 the Museum of the Kansas State University, at Lawrence, 

 Kansas. 



In June, 1872, Professor Marsh ^ published some notes about 

 the skull' 



1. Position of the Quadrate Bone. — The quadrate, which had 

 been placed by Cope and Marsh on the wrong side, receives its 

 correct position. 



2. Discovery of the Stapes. — The stapes is described as a 

 slender rod, nearly round, expanded proximally, and to some 

 extent also at its distal extremity. " The proximal extremity 

 was probably in the fenestra ovale, and its distal end in the 

 meatal pit of the quadrate." 



3. Discovery of the Columella. — A slender cylindrical bone is 

 considered as the columella (epipterygoid). The bone is some- 



1 Marsh, O. C, A^otice of Some New Fossil Reptiles from the Cretaceous and Terti- 

 ary Formations, Am. Journ. Sci., Vol. I, June, 187 1. 



2 Snow, F. H., On the Dermal Covering of a Mosasauroid Reptile {Liodon dyspe- 

 lor), Trans. Kan. Acad, Sci., Vol. VI, 1878, pp. 54-58, Fig. 



3 Marsh, O. C, On the Structure of the Skull and Li?nhs in Mosasauroid Rep- 

 tiles, Am. Journ. Sci., Vol. Ill, 1872. 



