EASTMAN: THE DINICHTHYIDS. 35 
has much in common with the type of dorso-median described by Trautschold 
as Pelecyphorus, but may best be considered as representing a distinct species. 
Formation and Locality. — Devonian; Livonia and Government of St. 
Petersburg. 
Dinichthys trautscholdi nomen nov. 
1889. Coccosteus megalopteryx, H. Trautschold, Ueber Coccosteus megalopteryx, 
etc. (Zeitschr. deutsch. geol. Gesellsch., Vol. XLI. pp. 38-45, Plate Y, 
Figs. 1-6.) 
1890. Coccosteus megalopteryx, O. Jaekel (Neues Jahrb., Vol. II. p. 145). 
1890. Pelecyphorus, H. Trautschold (Zeitschr. deutsch. geol. Gesellsch., Vol. XLII. 
. 576). 
1891, ds ÓN G. Giirich, Ueber Placodermen und andere Fischreste im 
Breslauer mineralogischen Museum (Zeitschr. deutsch. geol. Gesellsch., 
Vol. XLIII. p. 906). 
1896. Dinichthys trautscholdi, C. R. Eastman, Observations on the Dorsal Shields 
in the Dinichthyids (Amer. Geol., Vol. XVIII. p. 222). 
The type specimens represented in Plate V. Figs. 1-6 of Trautschold’s paper 
on Coccosteus megalopteryx (loc. cit., 1889), are now preserved in the Breslau 
Museum. They are from the Devonian of the River Ssjass, in Northwest 
Russia, and are apparently very closely related to the foregoing species. The 
principal differences consist in the larger size and less strongly arched condi- 
tion of the dorso-median proper, and- the different shape and position of the 
carinal process. The latter is more deeply excavated on its posterior face, 
stands nearly at right angles with the surface of the shield proper, and is 
given off from it slightly in advance of the hinder margin of the same. In 
this last respect we find a resemblance to the dorso-median described by New- 
berry as D. precursor; and, as in most American species, the process bears dis- 
tinct traces on its inferior surface of the attachment of muscles (Trautschold, 
loc. cit., Plate V. Fig. 6). On the other hand, Coccosteus-like affinities are 
shown by the tuberculated surface of the dorso-median, and by the presence 
upon it of sensory canals. These curve around toward one another posteriorly, 
but are not continued across the middle of the shield. The development of 
the inferior ridge and its terminal process is very pronounced. The dimen- 
sions of the largest process observed by Trautschold are stated to be 6.5 cm. 
in height by 3 cm. in width at the base, — proportions which are eminently 
Dinichthyid. 
This species, which it seems proper to name in honor of its original de- 
scriber, Professor Trautschold, was confused by this author with a Selachian 
ichthyodorulite which he mistook for a swimming appendage of Coccosteus. 
Later, when it was pointed out that Coccosteus could not properly include 
either of these forms, a new generic title was proposed for each, — Megalopterix 
for the ichthyodorulite (afterwards discovered to be identical ‚with Psam- 
mosteus), and Pelecyphorus for the dorsal shields, Curiously enough, the 
