No. 2. — On the Relations of Certain Plates in the Dinichtliyids, 

 with Descriptions of New Species. By C. E. Eastman. 



The present contribution may be regarded as a continuation and 

 enlai'gement of two previous articles on the Dinichtliyids,-' 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 Dinichthys ; 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 Zool- 

 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. intermedins 

 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 intermedins 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, 22.3). 



2 Newberry, J. S., Palajozoic 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. 



