242 AVES. 



fourth trochlea slightly longer than the second, and a large perforation 

 in the groove between the third and fourth trochlea. The typical species 

 is Gastornis parisiensis, founded on a tibio-tarsus about 0'5 m. in length 

 from the Lower Eocene (Argile Plastique) of Meudon, near Paris ; a femur 

 and other fragments from the Paris basin are ascribed to it. Similar 

 portions of the hind limb from the Woolwich and Reading Beds, near 

 Croydon, Surrey, are named G. klaasseni. The G. edwardsi, already 

 referred to, occurs in corresponding beds near Rheims, France, and at 

 Mesvin, near Mons, Belgium. 



ORDER 2. CARINAT^E. 



The earliest distinctly carinate birds of which there is as yet 

 any precise information are the toothed genera, Ichthyomis and 

 Apatornis, from the Upper Cretaceous of North America. They 

 constitute the extinct 



Sub-Order 1. Odontormce. 



The teeth are fixed in distinct sockets, hence the name 

 ODONTORMCE. The mandibular rami are not anchylosed at the 

 symphysis ; and the vertebrae are all amphicoelous (biconcave). 



Ichthyomis (fig. 145). This is a small bird, known by imperfect 

 skeletons. The bones are delicate and more or less pneumatic. The 

 cranial bones are fused together, and the brain is relatively small. The 

 snout is elongated, and the pre maxilla? seem to have been toothless; but 

 teeth occur in distinct sockets in the maxilla and throughout the whole 

 length of the dentary bone. These teeth are laterally compressed, and 

 have vertical successors. Though the symphysial suture remains open, 

 the elements of the mandibular ramus are almost completely fused to- 

 gether. The quadrate bone is remarkable in exhibiting only a single 

 facette for articulation with the skull. The number of cervical vertebrae 

 is uncertain, but the third is interesting as showing a passage between 

 the biconcave and saddle-shaped form. There are six or seven dorsals, 

 ten vertebrae comprised in the sacrum, five free caudals, and a small, 

 though typical pygostyle. The clavicles are unknown, but the remainder 

 of the pectoral arch is proved to be like that of a normal bird of flight, 

 and the wing is well-formed, the humerus bearing an enormous pectoral 

 crest. The pelvis is relatively small, and all its elements are fused to- 

 gether. There is a moderately large acetabular perforation, while both 

 ischium and pubis are free at their distal end. The femur is long and 

 slender, the tibio-tarsus still longer, without a bridge over the groove 

 for the extensor tendons ; the completely formed tarso-metatarsus is 

 short, and the fibula much reduced. Ichthyomis has hitherto been 

 found only in the Cretaceous of Kansas, and perhaps of Texas, U.S.A., 



