40 Reviews — U. S. Geological Survey — 



small type as Ballo-pns. Both these are probably near relatives of 

 Compsognathus. from the Lithographic Stone of Solenhofen (plate 

 Ixxxii; and Geol. Mag. 1896, PI. I, and p. 392, Fig. 2). These 

 are among the smallest of the class. 



One of the largest carnivorous forms was Ceratosatirus [C. 

 nasicornis, Marsh), measuring some 18 ft. in length and standing 

 nearly 15 ft. from the ground. It had a horn-core on the nasal 

 bone ; the bones of the pelvis are all co-ossified, as in existing birds ; 

 the metatarsal bones are also co-ossified, a feature characteristic of 

 birds, but not known hitherto in any other dinosaur. The pre- 

 maxillaries each contained three, and the maxillaries had each 

 fifteen, large, powei'ful, and trenchant teeth, clearly indicating, 

 as in our own Oolitic Megalosaurus, the ferocious character of the 

 animal. 



Of the other carnivorous dinosaurs of the American Jurassic, three 

 genera, Allosaurus, Creosaurus, and Lahrosaurus, are specially worthy 

 of notice. All were represented by species of large size, the natural 

 enemies of the gigantic herbivorous forms that were so abundant in 

 the same period. All had powerful jaws, sharp, cutting teeth, and 

 a flexible neck. The fore-limbs were quite small, and the feet 

 (manus and pes) were armed with strong claws for seizing living 

 prey. The hind-limbs were large and strong, and the animals used 

 them alone in ordinary locomotion. 



The herbivorous dinosaurs of the American Jurassic are of special 

 interest, comprising in the Sauropoda the most primitive and 

 gigantic forms, and also one of the most diminutive, Pleurocoelus. 

 The Atlantosauridfe include the largest forms ; the Diplodocidse and 

 Morosauridae are both represented by gigantic species ; whilst the 

 small Pleuroceelidse appear to be the last survivors of the order in 

 North America. 



Remains of the first three families are abundant in the AtJanto- 

 snurus beds of the West ; and the locality near Lake Como, in 

 "Wyoming Territory, has now become one of the most famous in 

 the entire Rocky Mountain region, having yielded to Professor 

 Marsh remains of several hundred dinosaurs. 



Atlantosaurus is only known from imperfect remains, but the 

 pelvic bones and femur of A. imwanis give an idea of its gigantic 

 size. The femur is over 6 ft. in length, and this, with the other 

 portions of the skeleton, indicates, says Marsh, an animal about 

 70 or 80 feet in length ! Apatosaurus is a nearly allied genus. 

 In Brontosaurus, the type-specimen being a nearly entire skeleton, 

 we obtain by far the most complete and accurate knowledge of 

 any of the Sauropoda yet discovered. In Atlantosaurus and Apato- 

 saurus there are only three coalesced sacral vertebree, in £rontosauriis 

 there are five. Although about 60 ft. in length, its skeleton is 

 distinguished by the peculiar lightness of its vertebral column, 

 the cervical, dorsal, and sacral vertebrae all having very large 

 cavities in their centra; the first three caudals, also, are lightened 

 by excavations in their sides. 



The head of Brontosaurus was remarkably small ; the neck was 



