50 
DAVIS : FOSSIL FISH EEMAINS. 
Messrs. St. John and Worthen. Though very closely related to 
Orodus the authors consider that minor differences are sufficiently 
distinctive to form the new genus Agassizodus for the accommoda- 
tion of the specimens. About four hundred and fifty to five 
hundred teeth comprised the whole of the left ramus of the lower 
jaw and a portion of the right one. In their description of this 
remarkable specimen the authors state that "the articular extrem- 
ities of the jaw are not preserved, though fragments of the substance 
of the cartilage are scattered through the rock mass upon which 
the teeth are imbedded. These cartilages were doubtless com- 
paratively thin, the outer and inner folds giving way to the 
pressure which flattened the rami, as shewn in the present 
condition. The teeth are disposed in serial rows having a 
convoluted inrollment from the inner to the outer border, and 
gradually increasing in size from the posterior extremity to the row 
of large median teeth, anterior to which the rows as regularly 
diminish in size towards the symphysis," the posterior portion of 
the jaw has six to nine rows of teeth similar in form to, but of 
smaller size than the teeth of the median portion. The middle 
portion of the ramus is occupied by a row of proportionately very 
large teeth which differ from the posterior teeth in having the 
crown produced into a strong, obtusely conical excentric prominence 
which culminates at a point more or less posterior of the middle of 
the tooth, whilst the posterior teeth are devoid of any defined 
median keel. The anterior portions of the teeth are very similar 
to those situated posteriorly of the median row. There are eight to 
nine rows, and contrary to the posterior ones they gradually 
diminish in size anteriorly as they approach the symphysis of the 
jaw. In the extreme anterior rows the teeth assume considerable 
diversity of form, and there are a number of minute, nearly 
circular teeth which exhibit in the form of the crown, and its 
sculpturing a strong likeness to Petrodus. " Generally considered, 
the teeth present the closest affinities with Orodus Ag., a group 
prevalent in the Lower Carboniferous formation." But the present 
