No. 514] DIN It'll Til Y1D A MM ON PLATES 



593 



described by Von Koenen 4 and referred with doubt to 

 D. minor. In this case the material was too poorly pre- 

 served to admit of the exact determination of the dif- 

 ferent bones. In the second specimen the preservation 

 is quite satisfactory and we are indebted to Dr. Eastman 5 

 for its description. He has referred it tentatively to 



D. newberryi Clarke. This latter example shows all six 

 of the ventral plates but little removed from the original 

 position. In his restoration Dr. Eastman illustrates 

 the conditions of overlap and brings the bones into the 

 positions which it is believed they occupied in life. 



Comparing now (Fig. 3) the restoration of D. new- 

 berryi (?) with that here regarded as D. halmodeus it 

 will be seen that in each case the antero-ventrolateral 

 overlaps the postero-ventrolateral and that all four 

 ventrolaterals overlap the two median plates. When, 

 however, the relations of the two medians are considered 

 we are unable to carry the comparison farther. In D. 



* A. von Koenen. Ueber einige Fischreste des norddeutschen und 



pp. 1-37, Plates I-IV, 1895. 



• C E. Eastman. On the Relation of Certain Plates in the DinfchttyM* 

 Bull. Mus. Comp. Zool. Harvard, Vol. XXXI, October, 1897, pp. 26 and 27, 

 Plate I, fig. 2 and Plate IV. 



