MEGALONYX LEIDYI, N. SP. 7 



abuts on the front wall just described and participates in forming the apex of its 

 triangular process. 



The upper bony septum of the cavity is formed by a perpendicular lamina, 48 

 mm. high and 2 to 4 mm.- thick in its anterior margin. This lamina, which extends 

 115 mm. backward, has its free edge grooved for the attachment of the cartilaginous 

 septum. The distance between the antero-inferior corner of this lamina and the apex 

 of the triangular process below is 2G mm. The anterior margins of the nasal bones 

 project about 25 mm. beyond the perpendicular lamina. Attached to the intero- 

 inferior margins of the nasals, and about 30 mm. behind their anterior margins, ap- 

 pear the anterior margins of the ethmo-turhinals as vertical laminae, until in the 

 postero-supci'ior recesses of the cavity, they expand their convolut'ed portions. 



The maxillo-turbinals are very large. Their anterior extremities show them to 

 be borne on the lateral walls of the cavity, near the proximal extremity of the canine 

 molars, and thence to extend both upward and downward. The upper portion bends 

 around the alveole and bulges out externally, following, with a small interspace, the 

 form of the wall of the cavity. The lower portion extends into the cavity between 

 the maxillary wall and the nasal crest. The inner side facing the narial septum is 

 flattened. The vertical height of the whole maxillo-turbinal is at least 8 cm., the 

 upper portion being the higher ; the antero-posterior diameter is about 9 cm. At 

 the anterior margin of its root on the maxillary wall is seen a circular foramen with 

 raised borders, appearing as the projecting end of a tube. 



Capacious air sinuses extend backward in the root of the pterygoid (PI. Ill), and 

 branch off from there forward into the alveolar wall of the maxilla. 



Inferior view, and sections of the shull. — The distinctive characters of M. leidyi 

 are best expressed in its proportions. Leaving out measurements and plates from 

 Leidy's "Memoir," his description would exactly fit to our specimen, as well. Per- 

 haps the most striking peculiarity of the latter is the far lesser prominence (depth) 

 of its maxillary portion. This will be most readily appreciated by comparing the 

 sections, PI. V, Figs. 1-6, which were constructed with great care. Pigs. 1, 3 and 5 

 from the Kansas specimen, and Figs. 2, 4 and 6 from a plaster cast of the Owen 

 specimen. 



Sections 1 and 2 were taken vertically and longitudinally through the sagittal 

 crest. The vertical distance between the base of the cranium and the most projecting 

 point of the hard palate in the specimens measured, is respectively 31 mm. and GO mm. 



Sections Sand 4 are transverse, nearly vertical, sections of the same specimens, 

 immediately in front of their 2d molars and anteorbital mai'gins. 



Sections 5 and 6 are also transverse and vertical, passing through the anterior 



