696 PROF. OWEN ON THE RANK AND AFFINITIES IN 



fore part of the premaxillary (fig. 15, 22) in the Mosasaurians is sub- 

 triangular as in Varanus, and forms a more definite and larger propor- 

 tion of the fore end of the skull than in Python; it supports on its under 

 flattened surface two pairs of teeth, smaller than the maxillary ones ; 

 laterally it is suturally connected with the maxillaries (21). From 

 the middle of the upper convex surface of the premaxillary there 

 extends backward and slightly upward a nasal process (fig. 15, 22') 

 relatively as long as in Varanus, with the pointed apex terminating 

 between the nasals. These bones (ib. 15) are continued, separately, 

 a short way forward below the nasal process of the premaxillary ; 

 but the median suture, penetrated by that process, is soon obliterated 

 in the nasals, at least of Mosasaurus Hoffmanni. These are thus 

 continued backward as a single bone slightly expanding ; and they 

 are notched to receive the antero-median points of the frontals, 11, each 

 of which is continued forward a short way along the side of the 

 nasal, contributing a small portion to the periphery of the external 

 nostril, and is there interposed between the nasal (15) and maxil- 

 lary (2i) ; further back the frontal joins the prefrontal (U). There 

 is no trace of this premaxillo-naso-frontal structure in Ophidia ; it 

 is a Lacertian characteristic ; and the modification shown in Mosa- 

 saurus most nearly resembles that of the Varanus and Monitor 

 amongst existing Reptilia. 



Prof. Cope diagrammatically indicates the most instructive features 

 of this lacertian characteristic in the Mosasaurians which he refers 

 to his genera Glidastes and Platecarpus * ; but he omits the sutures 

 which in Mosasaurus Hoffmanni and Mosasaurus Maximiliani define 

 the nasal bones. 



The more perfect example of the skull of the latter North-Ame- 

 rican species affords satisfactory demonstration of this strong diffe- 

 rential character as between the Lacertians and Ophidians. 



The locality of this skull, as noted by its acquirer, brings it 

 within the Cretaceous series of the United States. The internasal 

 suture persists in Leiodon anceps, fig. 15. 



§ 6. The bony Palate. — A State-officer in relation to the Indians 

 of the Upper Missouri obtained the fossil at the " Big- bend of the 

 river, between Fort Lookout and Fort Pierre," and brought it to 

 St. Louis, where it was noticed by Prince Maximilian of Neu-Wied f, 

 in the officer's garden, and was presented to the Prince, who brought 

 it over to Europe and deposited it in the Museum at Bonn. This 

 specimen afforded the subject of Prof. Goldfuss's excellent mono- 

 graph J, in which the components of the bony palate, not yielded by 

 Cuvier's specimen, are supplied. The illustration of this structure 

 in fig. 16 is founded on the text and plate viii. of Goldfuss. 



The vomer (fig. 16, 13) is parial ; each lateral portion is 

 long and slender ; they diverge posteriorly as in the Monitor^, 

 before uniting, each by a similar angular suture, with the palatines. 



* Op. cit. plate xxxviii. 



t See his ' Keise in das Innere von Nordamerica,' Bd. i. p. 348. 



% " Dei* Schadelbau des Mosasaurus," &c, in the Acta Acad. &c, above cited. 



§ Cuvier, torn. cit. pi. xviii. fig. 3, 



