mabsh.] DETERMINATION OF GENERA. 201 



was considerably larger than the present type species and from a some- 

 what higher horizon in the Atlantosanrus beds. 



The type specimen here described, which pertained to an animal 

 about half as large as a domestic fowl, was found in Colorado. This 

 reptile was a contemporary of the carnivorous Hallopus, likewise one of 

 the most diminutive of dinosaurs, and one of the most remarkable. 



DETER3IIXATIOX OF GEXERA. 



The various dinosaurs thus briefly referred to under their respective 

 genera have many other points of interest that can not be here dis- 

 cussed, but their resemblance to birds is worthy of some notice. This 

 is apparent in all of them, but in the diminutive forms the similarity 

 becomes more striking. In all the latter the tibia is longer than the 

 femur, a strong avian character, and one seen in dinosaurs only in the 

 small bird-like forms. 1 In Nanosaurus nearly all, if not all, the bones 

 preserved might have pertained to a bird, and the teeth are no evidence 

 against this idea. In the absence of feathers an anatomist could hardly 

 state positively whether this was a bird-like reptile or a reptilian bird. 



The main characters of the four genera above discussed are as follows: 



CA3IPTOSAFRTJS. 



Premaxillaries edentulous, with horny beak. Teeth large, irregular, 

 and few in number. A supraorbital fossa. Cervical vertebrae long and 

 opisthoccelous. Lumbars present. Five vertebrae in sacrum, with 

 peg-and-notch articulation. Sternum unossifled. Limb bones hollow. 

 Fore limbs small. Five functional digits in manus. Prepubis long 

 and broad ; postpubis elongated. Femur longer than tibia. Metatar- 

 sals short. Three functional digits in pes, the first rudimentary and 

 the fifth wanting. 



DBYOSAURTJS. 



Premaxillaries edentulous, with horny beak. Teeth of moderate size. 

 A supraorbital fossa. Cervicals long and biconcave. No lumbars. 

 Six coossified vertebras in sacrum, without peg-and-notch articulation. 

 Sternum unossifled. Limb bones hollow. Fore limbs very small. Five 

 digits in manus. Prepubis long and narrow; postpubis elongate and 

 slender. Posterior limbs very long. Femur shorter than tibia. Meta- 

 tarsals long and hollow. First digit in pes complete ; fifth metatarsal 

 represented by short splint only. 



LAOSAURUS. 



Premaxillaries edentulous. Teeth small and irregular. Cervicals 

 short and flat. Six coossified vertebra? in sacrum; no peg-and-notch 

 articulation. Sternum unossifled. Fore limbs small. Limb and foot 

 bones hollow. Prepubis very short and pointed; postpubis slender. 

 Femur shorter than tibia. Metatarsals elongate. First digit in pes 

 functional: fifth rudimentary. 



1 Besides the genera here mentioned, Cceluras, Compsognathus, and Hallopus also possess this 

 character. 



