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POPULAR SCIENCE REVIEW. 
sulphate, the tube acquired no increase of weight. This nitrogen, entirely 
freed from oxide, was now passed over cold spongy platinum, mixed with 
hydrogen, and 3 milligrammes of ammonia were produced in an hour. But 
when the mixed gases were passed over heated asbestos before reaching the 
platinum, no ammonia was produced until the asbestos-tube had cooled con- 
siderably. Hence the author concludes that nitrogen, like phosphorus, may 
exist in two states, active and inactive, the latter produced by exposure to 
heat. ( Journ . Chem. Soc., March 1881, pp. 128 and 130.) 
GEOLOGY AND PALAEONTOLOGY. 
Classification of Dinosaurs . — Prof. Marsh describes the characters pre- 
sented, by a nearly complete skeleton of the gigantic Dinosaur, named by 
him Brontosaurus excelsus, and indicates a second species of the same genus 
(i?. amplus ) of about the same size, and several other forms of the same 
order from Jurassic deposits in the United States. He remarks that the 
collection of American Jurassic Dinosaurs in the Museum of Yale College, 
includes the remains of several hundred individuals, many of them in 
excellent preservation. The series is so complete, that he thinks it may 
serve as a basis for a provisional classification of the American Jurassic 
forms, which may be hereafter extended to include the Dinosaurs from other 
formations in America, and those of other countries. Of this proposed 
classification he gives the following outline : — 
Order DINOSAURIA. Owen. 
1. Sub-order Sauropoda (Lizard foot). Herbivorous. 
Feet plantigrade, ungulate ; five digits in all feet. 
Pubes united in front by cartilage ; no post-pubis. 
Precaudal vertebrae hollow ; limb bones solid. 
Family Atlantosauridce. 
Genera Atlantosaurus, Apatosaurus, Brontosaurus, Diplodocus, 
and Morosaurus. 
2. Sub-order Stegosauria (Plated Lizard). Herbivorous. 
Feet plantigrade, ungulate ; five digits in all feet. 
Pubes free in front ; post-pubis present. 
Vertebrae and limb bones solid. 
Fajnily Stegosauridce. 
Genera Stegosaurus. 
3. Sub-order Ornithopoda (Bird foot). Herbivorous. 
Feet digitigrade ; four functional digits in the fore, and three in 
the hind foot. 
Pubes free in front ; post-pubis present. 
Vertebrae solid; limb bones hollow. 
Family Camptonotidce. 
Genera Camptonotus, Diracodon, Laosaurus, and Nannosaurus. 
