CRANIAL OSTEOLOGY OF THE PANTODONTIDiE. 2/5 



two closely approximated rows : the teeth are pointed and 

 exhibit a very slight curvature ; they are larger than those of 

 the premaxilla. The front part of the maxilla is rigidly fixed to 

 the outer side of the palatine ; there is an important articulation 

 between the maxilla and the under side of the prefrontal, aud a 

 slight articulation between the anterior extremities of the 

 maxillary aud nasal bones. There is no surmaxilla. 



The mandibular ramus is long and slender ; the coronoid 

 process is situated very far back, and the upper edge of the 

 dentary is toothed from the symphysis to the base of this process. 

 The teeth are set in two closely-set rows, like those of the 

 maxilla, except that the largest teeth are in the outer row, 

 whereas in the maxilla the largest belong to the inner row. 



The hyomaiidibular articulates with the cranium by a single 

 head. There is no visible suture between the palatine and the 

 ectopterygoid ; the entopterygoid extends well forward along the 

 inner edge of the palatine, almost to the extremity of that bone. 

 The entopterygoid is thick in the region of the groove in which 

 the parasphenoidal peg is received, and this part of the bone bears 

 strong, curved, pointed teeth, nearly as large as those on the 

 parasphenoid. Smaller teeth occur on the ectoptery go-palatine 

 bone, a long outer row (really a double row, like the dentition of 

 the maxilla) extending back almost to the quadrate articulation, 

 and a shorter inner row. 



The opercular is reduced in size and lies along the upper two- 

 thirds of the preopereular ; its width is about two-fifths of its 

 height. There is no subopercular. Several branchiostegal rays 

 are missing from the specimen examined : Peters {I. c. p. 196) 

 puts the number as eleven, and Boulenger (I. c. p. 120) as nine. 



The interhyal is large and ossified ; there is a small upper 

 hypohyal, but no lower ; the urohyal is very small. Above the 

 glossoliyal cartilage and the basibranchials * is a large, triangular, 

 deutigerous bony plate, concave on its upper surface, recalling 

 the similarly placed lingual bone of Osteoglossum, except that the 

 width of the hinder part is greater, and that the largest teeth 

 occur in the median line of the plate. Situated behind this, and 

 lying over a tract of cartilage, is a small, circular, dentigerous 



* No basibranchials are to be seen beneath the dentigerous plate in the 

 specimen examined; they may have been removed in the preparation of the 

 skull, or possibly their absence is to be explained by the basibranchial cartilages 

 failing to ossify. 



19* 



