128 Reviews—Prof. K. v. Zittel’s Palichthyology. 
the affinities of the family. The characters of the pectoral fins, 
indeed, would justify its being placed in a much more isolated 
position than that it occupies, as already suggested by Cope’ from 
features in the structure of the skull, and lately by C. Brongniart? 
from more general considerations. Xenacanthus, Pleuracanthus, and 
Orthacanthus are separately described; though, with Mr. J. W. 
Davis,* we fail to appreciate the distinctive features. 
The Squatinidz introduce the series of tectospondylic Selachians. 
This family is first recorded from the Lithographic Stone of Bavaria, 
and in addition to the ordinary recognized species of this age, the 
author includes the fragmentary fossil from the corresponding 
formation in Ain, France, named Phorcynis catulina by Thiolliére. 
A figure of a most perfect example of Squatina alifera from Hich- 
statt is given, showing for the first time that the median fins are 
arranged precisely as in the living species. 
At this point Dr. von Zittel defines and explains the “ Unter- 
ordnung Batoidei” (mainly after Giinther), and includes therein 
the remaining Selachian families. The Pristide (Saw-fishes) are 
believed to be represented by vertebra in the Chalk (very doubt- 
fully determined), but remains of the characteristic snout have not 
hitherto been recognized from beds below the Eocene. Most of the 
latter fossils are referred to Pristis, and a few from Hgypt to 
Propristis, Dames. To these may now be added Amblypristis, 
Dames (antea p. 28). 
The definition of the Pristiophoridee demonstrates the illogical 
nature of the “ Unterordnung,” one family-character being noted as 
“ Kiemenoffnungen seitlich gelegen, nicht auf der Unterseite,” while 
on the previous page exactly the reverse (‘‘ Kiemenspalten auf der 
Unterseite””) occurs unqualified in the definition of the major 
division. Only doubtful vertebra of Pristiophoride are known 
from the Tertiaries; but the Liassic Squaloraja polyspondyla is also 
assigned to this family—a position from which later researches have 
necessitated its removal.* 
The Psammodontide are an extinct family of Rays with great 
crushing teeth, confined to the Carboniferous period, and the sym- 
metrical teeth named Copodus are placed here equally with the more 
typical paired teeth of Psammodus itself. Nothing, however. is 
known of these fishes beyond their fragmentary dentition. The 
Petalodontide, of Carboniferous and Permian age, are a little more 
satisfactorily understood, a portion of the body of one genus, 
Janassa, having been discovered in the Continental Kupferschiefer. 
Teeth like those named Vetalodus are exclusively adapted for 
cutting, while in the most specialized genus, Janassa, the coronal 
edge is blunt and overturned, so that the dentition is admirably 
suited for crushing and trituration. Fig. 109 ought to be named 
Polyrhizodus magnus, McCoy; and the tooth shown in fig. 111 
1 Proc. Amer. Phil. Soc. 1884, p. 577. 
2 Comptes Rendus, April 28rd, 1888. 
5 Quart. Journ, Geol. Soc. vol. xxxvi. (1880), p. 321. 
4 Proc. Zool. Soc. 1886, p. 527. 
