0. C. Marsh — Ornithopoda of the American Jurassic. 87 



and it would be difficult to tell many of the isolated remains 

 from those of birds. A larger species, which may be called 

 Laosaurus consors, is now known by several skeletons nearly 

 complete. The type specimen, here figured in part on Plates 

 Y-YII, is the most perfect of all, and this was collected by 

 the writer in 1879. The animal when alive was about eight or 

 ten feet in length. The known remains are from the Atlanto- 

 saurus beds of Wyoming. 



One of the distinctive features of this genus, which sep- 

 arates it at once from those above described, is the pubis. 

 The prepubis, or anterior branch of this bone, which was very 

 large and broad in Ca?nptosaicrus, still long and spatulate in 

 Dryosaurus, is here reduced to a pointed process not much 

 larger than in some birds. These differences are shown in 

 Plate VII, figures 1, 2, and 3. 



Nanosaurus, Marsh, 1877. 



The smallest known Dinosaur, representing the type species 

 of the present genus, was described by the writer in 1877, 

 under the name Nanosaurxis agilis* The type specimen con- 

 sists of the greater portion of the skull and skeleton of one 

 individual, with the bones more or less displaced, and all en- 

 tombed in a slab of very hard quartzite. The whole skeleton 

 was probably thus preserved in place, but, before its discovery, 

 a part of the slab had been split off and lost. The remaining 

 portion shows on the split surface many important parts of 

 the skeleton, and these have been further exposed by cutting 

 away the matrix, so that the main characters of the animal can 

 be determined with considerable certainty. 



A study of these remains shows that the reptile they repre- 

 sent was one of the typical Ornithopoda, and one of the most 

 bird-like yet discovered. A dentary bone in fair preservation 

 (Plate YI, figure 3) indicates that the animal was herbivorous, 

 and the single row of pointed and compressed teeth, thirteen 

 in number and small in size, forms a more regular and uniform 

 series than in any other member of the group. The ilium, 

 also, shown on the same plate, is characteristic of the Orni- 

 thopoda, having a slender, pointed process in front, but one 

 much shorter than in any of the larger forms. The posterior 

 end is also of moderate size. All the bones of the limbs and feet 

 are extremely hollow, strongly resembling in this respect those 

 of birds. The femur was shorter than the tibia. The meta- 

 tarsals are greatly elongated and very slender, and there were 

 probably but three functional toes in the hind foot. 



* This Journal, vol. xiv, p. 254, September, 1877. 



