374 University Geological Survey of Kansas. 



as well as the other teeth, is firmly anchylosed to the bone. 

 The ectopterygoid, which joins the palatine posteriorly, is a 

 long, thin bar of bone, with a number of teeth on the lower 

 border of an irregular size. The mandible is moderately deep, 

 and bears two series of teeth. Those on the internal side are 

 very large and situated far apart, while those on the external 

 side form a minute fringe. 



The succession of the teeth, as described by Professor Cope, 131 

 is very peculiar : "The first teeth appear on the alveolar sur- 

 face at a considerable distance apart. The second teeth appear 

 immediately in front of these, and by their presence create the 

 irritation which results in the absorption of the root and shed- 

 ding of the crown of the first. The teeth of the third series 

 appear in advance of the second, occupying the space between 

 them and the empty space previously occupied by No. 1. These 

 may coexist for some time with teeth No. 2, as the specimen 

 indicates, but the result is as before — the shedding of the 

 adjacent older teeth. In the case of the anterior long tooth of 

 each side, the movement is reversed. Here the successional 

 tooth appears behind the position of the functional, which is 

 consequently shed, and in the old fish this tooth occupies a 

 position behind a concave symphyseal portion, which is con- 

 cave and edentulous, or only provided with the small teeth of 

 the marginal row." 



The vertebrae are deeply grooved laterally. 



There are several bones of a single specimen which I refer to 

 this genus with doubt. These are figured on plate LXV, figs. 

 8, 9, and 10. The largest of these bones, fig. 8, is no doubt an 

 opercular. It is very thin, excepting near the anterior-superior 

 portion, where the bone is much thickened and presents an an- 

 terior and internal articular portion, for the hyomandibular, 

 and also another along the lower border, where there is a long 

 and narrow facet, probably for attachment of one of the other 

 opercular bones. This bone is finely striated both externally 

 and internally. 



The second of these bones, fig. 9, presents an articular facet 



131. Cret. Vert. West, p. 301. 



