Il8 NEW YORK STATE MUSEUM 



It is inconceivable that this fixed spinous appendage is any way homolo- 

 gous with the jointed pectoral limbs of Asterolepids. Plates not unlike 

 those of the present species have been described by Traquair from the 

 Lower Devonic of the Eifel district under the name of A. pruemensis. 

 The so called A. decipiens of Smith Woodward, from the Lower 

 Devonic of Spitzbergen, appears to be of different nature. 



Formation and locality. Onondaga limestone ; Leroy, N. Y., and 

 equivalent formation of Ohio. 



Genus dinichthys Newberry 

 It is difficult to frame a satisfactory diagnosis of this genus which shall 

 enumerate its principal characters and at the same time enable one to draw 

 a rigid distinction between its various species and those of Coccosteus. 

 The fact is, the two genera are most intimately related, and though their 

 terminal members are sufficiently well characterized, they are connected by 

 insensible gradations. The typical species of Dinichthys represent unques- 

 tionably a later and more advanced stage of specialization than that with 

 which Ave are familiar in Coccosteus decipiens, for example; but 

 between these extremes lies a host of intermediate forms. Evidence of 

 specialization in forms like D. herzeri, D. terrelli etc. is strikingly 

 apparent in their gigantic size, the head shield measuring nearly a meter 

 across, and their massixe and cumbersome armor being unrivaled amongst 

 fishes. As a necessary accompaniment of increase in size, the cranial plates 

 become more intimately fused in the adult, the articulations between head 

 shield and abdominal armor more complicated, and various minor modifica- 

 tions are to be seen in the dentition and arrangement of the body plates. 

 Nevertheless, in spite of hypertrophic enlargement of all the parts, there is 

 everywhere a surprising conformity to the basal type of Coccosteus. It 

 is necessary to insist upon this close correspondence, which has hitherto 

 escaped attention (owing to faulty restorations and other reasons), and 

 possibly even now might be questioned by those who have not actually 

 compared the different parts. 



