22 CATALOG OF FOSSIL FISHES IN THE MUSEUM 



tion of the markings resemblijig a fingerprint, except that the lines are 

 all discrete and do not join. In this central portion of the ornamenta- 

 tion, the lines parallel to the long axis of the plates are somewhat 

 recurved inward toward the centre of the plate. 



Remarks. — This species is represented by specimens of various sizes, 

 of which the type is the largest that has come under notice. It is the 

 second species to be described from America, the other being P. 

 delicatula Newberry (Paleozoic Fishes North Amer., p. 97, pi. xix, fig. 

 11), from the Chemung of Pennsylvania, from which it differs espe- 

 cially in ornamentation. 



The following specimens are all from the Rhinestreet shale (Portv 

 age), at Sturgeon Point, on Lake Erie. They were collected by Mr. 

 F. K. Mixer. 



E 2039 Small elliptical plate 60 by 25 mm.; finely striated, the 

 striations following the contour of the edge. 



E 2040 Striated elliptical plate, 95 by 30 mm. (broken). 



E 2041 Small plate with fine striations rimning parallel to the mar» 



gin, 55 by 35 mm. 



PLACODERMATA 



In this catalog we adopt the view that the Antiarchi, the highest 

 division of the old group Ostracophori, and the Arthrodira, are 

 related. It seems impossible that such a remarkable correspondence 

 between the two groups in the arrangement of the armor of the head 

 and front portion of the body; in the head in both being movable on 

 the shoulder armor; in the agreement of the fundamental plan of the 

 dorsal armor plates; and the correspondence down to details in the 

 plan of the ventral armor, can be due to parallelism and not to 

 relationship. 6 



In this work we adopt the following arrangement of these primitive 

 forms: 



Placodermata (McCoy, 1848).'' 



1. Antiarchi (Bothriolepis, Pterichthys, etc.). 



2. Macropetalichthyida. 



3. Arthrodira {Coccosteus, Dinichihys, etc.). 



5 For a discussion of this subject see L. Hussakof: Studies on the Arthrodira. Mem. Am. Mus, 

 Nat. Hist., ix, 105-154, 1906, pis. xii, xiii; especially pp. 128-135. 

 '' An7i. and Mag. Nat. Hist., 2 ser., ii, i-io, 184S. 



