GEOLOGICAL MAGAZINE. 
NEW, SERIES! DECADE (fill... VOLE. VIL 
No. III.—MARCH, 1889. 
(Quswieuras, Aca NaS tenements. 
ns Na 
I.—On a New Specirs or Diprerus. 
By Dr. R. H. Traquair, F.R.S., F.G.S. 
(PLATE II.) 
ROM the Old Red Sandstone of Caithness, four species of 
Dipterus were originally named by Sedgwick and Murchison,} 
those being as follows :— 
1. Dipterus brachypygopterus, anal fin short. 
2. D. macropygopterus, anal fin long. 
3. D. Valenciennesit, small in size, narrow in shape. 
4. D. macrolepidotus, not characterized although figured. 
It is evident from the figures of “D. macrolepidotus” that it does 
not belong to the same genus, even to the same family, as the 
other forms. Those have circular scales, whereas in “ macrolepi- 
dotus,” the scales are rhombic, and the head bones are clearly seen 
to be very different from those of Dipterus. 
Nevertheless all the four “species” were reunited by Agassiz? 
into one, for which the name “macrolepidotus” was adopted, in the 
belief that the rhombic scales of that form were normal for the 
genus, and that their circular appearance in the others was due to 
wearing. 
McCoy, however, correctly recognized the circular contour of the 
. Scales in the true Dipteri, and rightly refused to recognize “ macro- 
lepidoius”’ as the type of the genus, or as a Dipterus at all, and in 
fact proposed to transfer it to Diplopterus.2 The other species 
proposed by Sedgwick and Murchison he restored to independence. 
In his “Footprints of the Creator,” Hugh Miller showed that 
Agassiz’s Polyphractus platycephalus was the head of a Dipterus,* 
and not a Placoderm, but he did not seek to identify it with any 
previously described species. 
Pander ® of course confirmed McCoy’s statement that D. macrolepi- 
dotus, of Sedgwick and Murchison, was not a Dipterus at all, but he 
reverts to Agassiz’s idea as regards the three other reputed. species. 
He united them again into one, for which he preferred the name 
* Trans. Geol. Soc. 2nd ser. vol. iii. p. 148, tab. 15-17, 1829. 
” Recherches Poissons Foss. Tome i. 1835-43, p- 115. 
* Brit. Pal. Foss. Fase. ili. 1855, pp. 590-592. I have made “ macrolepidotus”’ 
the type of my new genus Thwrsius, Grou. Mac. November, 1888. 
4 1861 Kdition, p. 57. 
° Pander (Dr. C. H.) u. d. Ctenodipterinen d. Devonischen Syst. 1858, St. 
Petersburg, pp. 1-82. 
DECADE IlI.—VOL. VI.—NO. III. 7 
