TKACHODONTmE. 241 



Family TRACHODONTIM] 1 . 



Closely allied to the preceding family, but with the teeth arranged 

 in vertical rows, and articulating with one another so as to form a 

 more or less complete pavement. In the one genus (Diclonius 2 ) in 

 which it is known the skull is elongated and much depressed, and 

 the premaxillae are extended a considerable distance in advance of 

 the large nares, thus producing a very long edentulous portion. 



Genus ORTHOMERUS, Seeley 3 . 



Provisionally referred to this family. Known only by limb-bones 

 and caudal vertebrae, which appear to indicate a form closely allied 

 to Trachodon, but presenting some approximation to Iguanodon. 

 The caudal vertebrae (fig. 48) have their spines much inclined 

 backwards, and the anterior ones are more elongated* than in 

 Trachodon ; the chevron-facets are double, from which Dollo con- 

 cludes that the chevrons were open 5 . 



Orthomerus dolloi, Seeley 6 . 



The type species ; about the size of Trachodon foulki. 

 Hob. Europe (Belgium). 



The following specimens are from the Upper Cretaceous of Maastricht, 

 Netherlands, and belong to the Van Breda Collection. Pur- 

 chased, 1871. 



42955. The right femur, with imperfect extremities. Type (fig. 49, 

 (Fig.) A, B, C) ; figured by Seeley in the ' Quart. Journ. Geol. 



Soc' vol. xxxix. p. 249, fig. 2, A, B, C. Length 0,495 



(19-5 inches). 



1 =Hadrosaurid(B. 



2 See Cope, Proc. Ac. Nat. Sci. Philad. 1883, p. 97, pis. iv.-vii. 



3 Quart. Journ. Geol. Soc. vol. xxxix. p. 248 (1883). 



4 See Dollo, Bull. Mus. K, Hist. Nat. Belg. toI. ii. p. 211 (1883). 



5 Double facets are sometimes found in Iguanodon (Owen, ' British Fossil 

 Keptilia,' Dinosauria, pi. v.). 



6 Loc. tit. 



