486 Prof. 0. C. Marsh — On Jurassic Birds ^ their Allies. 



The presacral vertebrse are all, or nearly all, biconcave, resembling 

 those of Ichthijornis in general form, but without the large lateral 

 foramina. There appear to be twenty-one presacral vertebras, and 

 the same, or nearly the same, number of caudal s. The sacral 

 vertebrae are fewer in number than in any known bird, those united 

 together not exceeding five, and probably less. 



The scapular arch strongly resembles that of modern birds. The 

 articulation of the scapula and coracoid, and the latter with the 

 stei'num, is characteristic ; and the furculum is (.listinctly avian. 

 The sternum is a single broad plate, well ossified. It probably 

 supported a keel, but this is not exposed in the known specimens. 



In the wing itself the main interest centres in the manus and its 

 free metacarpals. In form and position these three bones are just 

 what may be seen in some j'oung birds of to-day. This is an 

 important point, as it has been claimed that the hand of Archoeopteryx 

 is not at all avian, but reptilian. The bones of the reptile are 

 indeed there, but they have already received the stamp of the bird. 



One of , the most interesting points determined during my investi- 

 gation of Archceopteryx was the separate condition of the pelvic 

 bones. In all other known adult birds, recent and extinct, the three 

 pelvic elements, ilium, ischium, and pubis, are firmly anchylosed. In 

 young birds these bones are separate, and in all known Dinosaurian 

 reptiles they are also distinct. This point may perhaps be made 

 clearer by referring to the two diagrams before you,^ which I owe 

 to the kindness of my friend Dr. Woodward, of the British Museum, 

 ■who also gave me excellent facilities for examining the Archmopteryx 

 under his care. In the first diagram we have represented the pelvis 

 of an American Jurassic Dinosaur allierl to Iguanodon, and here the 

 jDelvic bones are distinct. The second diagram is an enlarged view 

 of the pelvis of the Arcliasopteryx in the British Museum, and here 

 too the ilium is seen separate from the ischium and pubis. 



In birds the fibula is usually incomplete below, but it may be 

 co-ossified with the side of the tibia. In the typical Dinosaurs, 

 Iguanodon, for example, the fibula at its distal end stands in front 

 of the tibia, and this is exactly its position in ArchoBopteryx, an 

 interesting point not before seen in birds. 



The metatarsal bones of Archceopteri/x show, on the outer face at 

 least, deep grooves between the three elements, which implj'^ that 

 the latter are distinct, or unite late together. The free metacarpal 

 and separate pelvic bones would also suggest distinct metatarsals, 

 although they were placed closely together, so as to appear .connate. 



Among other points of interest in Arcliaiopderyx may be mentioned 

 the brain-cast, which shows that the brain, although comparatively 

 small, was like that of a bird, and not that of a Dinosaurian reptile. 

 It resembles in form the brain-cast of Laopteryx, an American 

 Jurassic bird, which I have recently described. The brain of both 

 these birds appears to have been of a somewhat higher grade than 

 that of Hesperornis, but this may have been due to the fact that the 

 latter was an aquatic form, while the Jin-assic species were land birds. 



^ The diaffi-ams referred to were exhibited at the York Meetiu'?, Brit. Association. 



