490 Professor H. G. Seeley — Dentition of Cynognathus. 



as a wedge which thins as it extends backward supporting the palatal 

 armature. There is no doubt that the tooth-plates met each other in 

 the median line of the palate without any sutural union or connection 

 between the contiguous maxillary bones other than the premaxillary 

 bones may have given. 



The inner median surface of the dental plate shows no indication of 

 sutural separation from the opposite maxillary bone, except in the 

 smooth base of the empty anterior socket. 



This inner surface of the plate is even, flat, with a straight base- 

 line, prominent above the contiguous maxillary bone, curving upward 

 as it extends forward. It is sub-parallel to the palatal dental crest ; 

 the depth of the dental plate is half an inch behind and oV inch in 

 front. This internal surface shines as though covered with a film of 

 enamel. It is finely pitted along its extent. It is roughened with 

 the contours of constituent denticles, of which there are more than 

 a dozen in a length of 2 inches, all welded together. Some are 

 triangular, and their points do not reach the palatal surface, while the 

 denticles between them, with exposed crowns, have ovate surface 

 contours on the summit-ridge of the palate. The appearance is that 

 of a mass of teeth densely packed in osseous union or cement. 



The fractured posterior surface is less clear than might have been 

 expected. It shows that the denticles are parallel to the inner 

 surface and to each other. They are vertical and form about six 

 rows, so that the individual teeth of the successive rows become 

 shoi'ter as they extend outward from the median line in harmony 

 with the incline of the dental plate. The obscure sections appear to 

 be narrow and cylindrical, but the teeth are probably of a flattened 

 ovate form in section, like the low crowns on the palate. 



On the palatal surface the denticles are arranged in parallel rows 

 (PI. XXIV, Fig. 1, P.T.), rising inward in successive tiers one behind 

 another. The short, low crowns have an ill-defined appearance of 

 being also arranged in rows which extend obliquely outward and 

 backward. Each crown is longitudinally ovate. They vary in size 

 and elevation and distance apart. Genei'ally the convex surface carries 

 one or two raised lines and a few granules which show no definite 

 plan of aiTangement. The rows of denticles become fewer as they 

 extend forward, and at the front of the principal plate are reduced to 

 three rows. At this point a fracture occurs, which appears to mark 

 a second dental plate, in which all the rows are gathered up into one 

 compressed elevated tooth-mass, about half an inch long. Its con- 

 stituent denticles appear to be worn with use ; they are close set, small, 

 ovate, oblique, and comprise two parallel rows. The narrow missing 

 tooth was shorter and may have had a similar structure. 



Having this remarkable armature on the maxillary bones, it was 

 important to re-examine the skull of Cynognathus crateronotus in the 

 Natural Histoiy Museum, and Mr. Richard Hall has so far removed 

 the matrix from the symphysial region of the mandible, with the 

 approval of Dr. A. Smith Woodward, as to demonstrate the presence 

 of teeth of a similar kind upon the maxillary plate of the palate, and 

 prove that this dental armature is one of the generic characters of 

 Cynogjtathus. 



