JOHAN Kl.KR. [SEC. ARCT. EXP. FRAM 



like forms. Palaeaspis, Pteraspis and kindred forms con- 

 -titule a related group. which give us a co-ordinate family Pteraspidae 



with a similar origin. 



Within the family Psammosteidae we can elucidate the development 

 h\ the erie.s '1'ln'ludnn J)r('p(uuispix Psn i niostcH s, which as 

 concerns the outer form of the body appears to constitute a parallel to 

 the series Tlielo'l/i* . l/r/ra.s/*/.v Akeraspis Cepltahixpix. 



( 'occosteidae. 



Great Coccossteomorpli form. 

 (PI. II, fig. 3 -4). 



The fish horizon at Skrap Valley provides us with a somewhat 

 large, beautifully ornamented skeleton plate. |S. I. 7). which is probably 

 a portion of a large, new Coccossteomorpli fish. 



Description. Figs .'! 4 on plate II give a better repi'esentatioa 

 then any long description can do of this specimen. The upper surface 

 is beautifully ornamented with large, round, slightly crenelated tuherd'--. 

 which often have a diameter of 2 mm. 



The borders of the plate appear to he the original one on three 

 -ides; on the fourth there is an irregular fracture line. On the smooth 

 inner >ide we see farthest down to the left a strongly developed facet, 

 hy which the plate must he assumed to have been superimposed over 

 an adjoining plate. 



The maximum length of the plate is 67 mm, At the edge which 

 i- seen turned up to be in the figure, the thicknes is 3 4 mm. 



Farthest to the right, where the plate however possibly has suffered 

 To-ion. this diminishes to 2 mm. and then rises to 7 mm. just m>ide 

 the broadest part of the facet. 



The plate is thus extre ly massive and >lroug. 



Observations. The determination of this plate has can-ed 



me a givat deal of lal ', although I have been unable to arrive at 



any entirely -ali^l'adory result. The sculpture may be said to he 

 i-nai^ely coccosleid. The inner structure agree.- entirely \\itli this con- 

 dition. Therefor it would appear to be certain thai we have before n- 

 a plate of a large COCCOSteomOTph lish. lint which? This <pie.-lion 

 i- not eas) to >ol\e. opedally when we |HP-V,.--. Mll -ood material IIT 

 \\ilh known forms to aid us in this task. 



