BY C. W. DE VIS. 



43 



specific form, so in the examples before us we can perceive an 

 approximate similarity in their leading features which enables us 

 to avoid the error of considering them all of different species and 

 leads us to regard them as not only one, but one with the living 

 C. Fosteri. They consist of four pterygopalatine plates and five 

 mandibulary : of the pterygopalatine of the upper jaw, one of the 

 left side is pretty complete, retaining the greater part of its 

 pterygoid element and the basal portion of the process for 

 articulation with the frontal cartilage, the utmost difference it 

 presents from the recent bone is the more forward position of that 

 process, which rises opposite the second anterior tooth instead 

 of opposite the interval between the second and third: the contour 

 of the inner edge of the dental is a continuous curve, as in the 

 recent fish. The surface of the plate in this specimen is nearly 

 smooth, but in the very young one accompanying it the surface is 

 even more pitted than its living exemplar. The two largest of 

 the mandibulary plates must have belonged to fish of considerable 

 size, that is, about four feet long, their plates are rather more, 

 elongated than in the living fish, and consequently, less curved on 

 the inner edge. In the best preserved the symphysial and 

 angular elements are retained in much completeness. It is 

 useless to dwell on the minute differences they show amongst 

 themselves, and when compared with the recent specimen. 

 Suffice it to say that after due consideration of the value to be 

 given to the dissimilarities, we must arrive at the conclusion that 

 one and all belonged to ancestors of the present species, 0. 

 Fosteri. 



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