JURASSIC VERTEBRATE FOSSILS. 485 



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 respecl 

 those of birds. The femur was shorter than the tibia. The metatarsals 

 are greatly elongated and very slender, and there were probably but three 

 functional toes in the bind foot. The remains now known indicate that the 

 animal when alive was about half the size of a domestic fowl. 



A second form referred by the writer to this genus, under the name of 

 Nanosaurus rex, may, perhaps, belong to the genus Laosaurus. The femur 

 is shown in fig. "J!i. The animal thus represented was considerably larger 

 than the present type species, and was found in a somewhat higher horizon 

 in the same region. 



BAPTANODON. 



In the horizon marked in the section as the Baptanodon beds the most 

 important known vertebrate is the large swimming reptile that has given 

 the name to these deposits, and figures of its characteristic remains are 

 given below as an aid in identifying the strata. This reptile, Baptanodon, 

 was most nearly allied to Ichthyosaurus, but was without teeth, and the 

 paddles had six digits, as shown in lig. 30 (p. 486). The vertebra', one of 

 which is represented in tig. 31, are verv similar to those of Ichthyosaurus. 

 Another interesting marine reptile from this horizon appears to be a true 

 Plesiosaur, with teeth, and has been described by the writer as Pantosaurus 

 Striatus. A vertebra of the type specimen is shown in fig. 32. A small 

 crocodile, Diplosaurus nanus, which the writer found in 1870 in the same 

 beds, was the lirst vertebrate discovered in this horizon. 



\ u \\ I i ISAURUS. 



In the succeeding Atlantosaurus beds a new and remarkable reptilian 

 fauna makes its appearance, and the gigantic Sauropoda are the prevailing 

 forms. In the Hallopus horizon the dinosaurs were, as already stated, the 

 most diminutive known, but in the present beds the representatives of this 

 group are the most gigantic land animals vet brought to light. The first 

 genus discovered, which has been named Atlantosaurus by the writer, 

 includes several species, all of huge dimensions. The lirst discovery was 



