1898-1902. No. 33.J UPPER DEVONIAN FISH REMAINS. 21 



According to HALL'S description Plitonia cylindrica is larger, from 

 26 30.5 mm. Tlie anterior end is possibly more rounded; the first 

 of his examples is depicted with a more pointed anterior. The extre- 

 mely fine radiating striae which HALL mentions in the case af Ph. 

 cylindrica appear to he quite lacking in the form from Skrap Valley. 

 He says, however, that these striae are frequently obsolescent and often 

 obsolete. 



Deviations in the dimensions are not of importance. The form from 

 Skrap Valley presumably lived in a brackish lake, and may therefore in 

 consequence be somewhat deformed. The other deviations are not in 

 my opinion of great importance. I shall not, however, venture to assign 

 the specimen to any other place than Phtonia cf. cylindrica HALL. 



H o r i / o n. Abundant in the fish horizon at Skrap Valley. Phtonia 

 cylindrica HALL is previously described from the Hamilton Group. 

 3 other species are known from the same horizon, 2 from Chemung. 



Pisces. 

 Psammosteidcie. 



It is very interesting to note that fragments of Psammosteus forms 

 belong to the most common fossils in the fish horizon at Skrap Valley. 

 For previously, this genus was known from Liv Land, Scotland, and 

 Spitsbergen only, and was quite unknown in the case of American 

 Devonian strata. 



Our knowledge of the genus Psammosteus is still extremely defective. 

 As is well known, Agassiz in his classic work "Recherches des poissons 

 fossiles", 1844, described several fragments of this genus from the Baltic 

 provinces of Russia. 



He gives 4 species which are distributed amongst the genera 

 Placosteus and Psammolepis. In a later work, "Poissons fossiles du 

 vieux gres rouge", (1845), he combined the latter in one genus which 

 was named Psammosteus. but at the same time he retained the four 

 species originally mentioned. As regards the systematic position of these 

 forms he gives no details. 



PANDER, who had a large quantity of material at his disposal, 

 in his important work "Die Placodermen d. devon. Systems" (1857) pp. 

 2024, gives a detailed account of these enigmatical fossils. He believes 

 that the species made are simply fragments of the same form, the 

 sculpture differing greatly in the various body plates. He also gives a 



