COPE ON GEOLOGY AND VERTEBRATE FOSSILS. 595 



toward the middle, and contained four teeth in a vertical column; the 

 longer grooves contained at least five. This estimate is based on a 

 specimen containing teeth described below. The vertical body contain- 

 ing the magazine is separated below from the walls of the deutary 

 bone by the large, open fissure of the Meckelian cartilage. This fissure 

 is open anteriorly as far as the middle of the dentigerous region, and 

 rises on the outer side of the magazine as it extends backward. Thus 

 it occurs that the magazine behind hangs freely suspended from its 

 superior border, and a portion of it extends even posterior to the poste- 

 rior extremity of the extero-superior border. This is due to the fact 

 that a huge coronoid process rises from the external plane of the 

 dentary bone, in front of the posterior extremity of the dental series, 

 the latter passing to its inner side in a manner not heretofore observed 

 among Eeptiles, but as is found in many Eodent Mammals. This pro- 

 cess is directed at right angles to the axis of the dentary bone, is quite 

 elevated, and is narrowed at the summit. Its base is concave behind, 

 its section forming neaiiy a half-circle. This concavity is continuous 

 with that already described as the place of Meckel's cartilage, but it is 

 also pneumatic in its functions. The dental canal enters, at its upper 

 part, the outer wall of the magazine, and traverses the bone between 

 the latter and the external surface of the dentary bone. The great 

 excavation of the posterior extremity of the dentary bone in connection 

 with the elevated hook-shaped coronoid give all these jaws an entirely 

 unique appearance. In this one, where the posterior border of the 

 coronoid process is completely preserved, I see no signs of suture 

 for coronoid, surangalar, or other bone. The base of the coronoid 

 process has such an extensive transverse diameter as to cause a great 

 widening at this region. The external face of the dentary is moderately 

 convex, and is perforated by rather distant foramina near the alveolar 

 margin. Viewed from the external side, the coronoid process is of nearly 

 equal and not great width, with rounded apex. From behind, it nar- 

 rows rapidly from a wide base, leaning somewhat inward, with convex 

 outer and plane inner faces. The posterior concavity contracts and 

 runs out upward. 



Measurements. 



M. 



Length of fragmeut of dentary bone 0. 'J80 



Depth of same at middle 0. 100 



Depth of magazine in front 0. 065 



Depth of magazine at middle „ 0. 080 



Width of dentary below at middle 0. 035 



Elevation of coronoid process 0. 120 



^. , ^ ., ( antero-posterior 0. OTO 



Diameter of coronoid process \ ^ ,, ,,.^ 



'■ < transverse 0.070 



Diameter (transverse) of six vertical grooves , 0. 040 



Eamus No. 2 was found by my assistant J. 0. Isaac. It belonged to 

 a rather larger individual than the last described, and agrees in general 

 characters with it. It differs iu the anterior continuation of the external 

 o B H 



