8 ODONTORNIT.HES. 



The preniaxillaries are elongate, and separate throughout their 

 jDOsterior two-thirds (Plate I, figure 5.) Their extremities touched the 

 frontals. Their sides are deeply excavated for the anterior nares, and in 

 front they are ankylosed, and form a long pointed beak, the end of which 

 is somewhat decurved. This extremity, back to the nasal openings, has its 

 surface pitted with irregular vascular foramina, indicating, apparently, that 

 it was once covered with a horny bill, as in modern birds. 



The various cranial characters above described may nearly all be 

 found in recent birds, if we search through different groups; but in 

 Hesperornis the stout maxillary bones were armed with well developed 

 teeth, a feature unknown in this class, before the discovery of the remains 

 described in the present volume. These teeth were set in a- deep continuous 

 alveolar groove, with only faint indications of separate sockets (Plate II, 

 figure 1.) They resemble most nearly, in form and structure, the teeth of 

 reptiles, and are fully described in the following chapter. There were no 

 palatal teeth, and none in the preinaxillaries. 



The Brain. 



The brain of Hesperornis was quite small, and more reptilian in type 

 than in any adult bird hitherto examined. On page 9, figure 1, the skull 

 in this g-enus is represented, with the outline of the brain-cavity in position. 

 The skull of the Loon is added in figure 2, also with a cast of the brain in 

 its natural position, and life size. A comparison of the two, places the 

 relative magnitude and proportions of the brain in each in strong contrast. 

 The reptilian type is shown on the same page in figure 3, which represents 

 in natural size a cast of the brain-cavity of a young Alligator. 



In Hesperomis regalis the olfactory lobes (figure 1, ol) were large and 

 elongate, and their nerves passed out of the cranium by separate orifices, 

 one on each side of the interorbital septum. The cerebral hemispheres 

 (figure 1, c) Avere of very moderate size, much smaller, proportionally, 

 than in any existing birds, and strongly resembling the corresponding part 

 in some reptiles. The two lobes were narrow, and sub-ovate in outline, 



