No. 2.— On the Relations of Certain Plates in the Dinichthyids, 
with Descriptions of New Species. By O. R. EASTMAN. 
Tam present contribution may be regarded as a continuation and 
enlargement of two previous articles on the Dinichthyids,! one of which 
discussed the relationships of certain detached and little known plates, 
and the other endeavored to trace the ancestry of the group. Some of 
the plates mentioned in the first paper are now illustrated and more 
fully described, together with others which afford additional evidence 
regarding the osteology of Dintchthys; and the views set forth in the 
second paper are now considered more in detail. In addition, descrip- 
tions are offered of several new species, and restorations are given of 
the dorsal and ventral aspects of Dinichthys. 
Unless otherwise stated, the material upon which all of the following 
descriptions are based is preserved in the Museum of Comparative Zoöl- 
ogy at Cambridge, Mass. To Mr. Alexander Agassiz, Director of the 
Museum, the most cordial and grateful thanks of the writer are due for 
the opportunity to study the collection, and to publish the results herein 
set forth. 
Dorsal Plates. — It is proposed to consider first the system of plates 
covering the dorsal surface of the body in Dinichthys. These plates are 
shown in their natural arrangement, as known to exist in D. intermedius 
and D. terrelli, in Plate 1, Fig. 1; their correspondence with homologous 
elements in Coccosteus and related genera will be obvious from an inspec- 
tion of the diagrams. The restoration here given may seem to call for 
a word of explanation, since it differs in certain respects from the familiar 
ones of Newberry and others.” The cranial osteology is based upon one 
of the most perfect heads of Dinichthys intermedius ever discovered, 
now the property of the Cambridge Museum. A full description of the 
1 Amer. Journ. Science, [4], Vol. II. pp. 46-50, July, 1896. Proc. Amer, Assoc. 
Adv. Science, Buffalo Meeting, August, 1896 (Abstract in Amer. Geol. Vol. XVIII. 
pp. 222, 223). 
2 Newberry, J. S., Paleozoic Fishes of North America (Monograph U. S. Geol. 
Survey, Vol. XVI. Plate LII. Fig. 2), 1889. Dean, B., Fishes, Living and Fossil, 
1895, p. 134, Fig. 134. 
VOL. XXXI. — NO, 2, 
