114 BULLETIN 89, UNITED STATES NATIONAL MUSEUM. 



Family SCELIDOSAIIRIDAE Huxley. 

 Genus HOPLITOSAURUS Lucas 1902. 



HOPLITOSAURUS MAESHI (Lucas) 1901. 



Plates 26-30. 



Stegosaurus marshi Lucas, Proc. U. S. Nat. Mus., vol. 23, 1901, pp. 591, 592, pk. 23-24. 

 HoplitosaunLs marshi (hvcAs) Science, new ser., vol. 16, No. 402, 1902, p. 435. — Lull, Amer. Jouin. 

 Sci., vol. 29, 1910, p. 30, fig. 7.— Zittel, K. A. Grundzuge der Palaentologie, pt. 2, 1911, p. 294. 



Type-specimen. — Cat. No. 4752 U.S.N.M. Consists of the right femur, proximal 

 half of left humerus; distal half of right humerus. Proximal portion of right 

 scapula and coracoid, one dorsal centrum, caudal centra, numerous dermal plates 

 of the spined, keeled, flattened, and rounded shapes; fragments of ribs and other 

 elements. Collected by N. H. Darton in 1898. 



Type-locality. — "Calico Canyon," near Bufl'alo Gap Station, South Dakota. 



Horizon. — I^akota, Lower Cretaceous. 



In 1901 Lucas first described this specimen as a new species of Stegosaurus. 

 but a year later, recognizing its affinities as being nearer the Wealden Polacanthus, 

 and therefore distinct from the former genus, he proposed the name Hoplitosaurus 

 for its reception. Since 1901 four genera and as many species of armored dinosaurs 

 have been described from the Cretaceous of this country; but in none of these arti- 

 cles is there reference made to the present form. It would appear on account of 

 the closeness of the geological horizons in which some of these specimens were 

 found that, when a comparative study is made, they will be found to be closely 

 allied, if not identical, with the present genus. 



The famih^ attribution of Hoplitosaurus in aU probability lies within the 

 Scelidosauridae of Huxley, an assignment which I beUeve will eventually include 

 other genera of American ridge-scuted dinosaurs. 



The original description by Lucas follows : 



The same Stegosaurus marshi is proposed for a new species of Stegosaur represented by a number 

 of plates, spines, and portions of the nuchal and gular armature, as well as by some vertebrae and bones 

 of the limbs, obtained by Mr. N. H. Darton in South Dakota from beds considered by him to be of 

 Lower Cretaceous age. 



This material, which is in the United States National Museum and is the type of the species, is 

 numbered 4752 in th6 catalogue of fossil vertebrates. It was found associated with remains of another 

 dinosaur of moderate size, probably related to Camptosaurus.' The species is characterized by the 

 general massive appearance of the plates and spines, the comparatively large extent of their basal sur- 

 faces, their abrupt taper, and sharp edges. In these respects they are quite different from the corre- 

 sponding portions of any other Stegosaur yet discovered, and coming, as they do, from the highest 

 horizon in which remains of Stegosaurs have been found they may be considered as representing the 

 latest developments in the dermal armature of this remarkable group of dinosaurs. 



A dermal spine found by Mr. J. B. Hatcher, in conjunction with remains of Triceratops, and 

 regarded at the time as belonging to that genus, may very likely have come from the species under 

 consideration. 



A spine, shown on plate [28], presumably from near tlie posterior end of the caudal series, has a long 

 and comparatively wide basal portion and then tapers rapidly to a spike-like form. 



A plate, shown on plate [29], apparently from the caudal series somewhat in advance of the spine 

 just described, is triangular in section, slightly rounded on one surface, while on the other it tapers 

 abruptly from the base with a concave curve. 



1 Type-specimen of Camptosaurus depressus Gilmore — C. W. Gilmore. 



