126 Reviews—Prof. K. v. Zittel’s Palichthyology. 
SELACHII. 
In the lengthy section upon the Plagiostomi (about 50 pp.), 
special prominence is given to the important researches of Kolliker 
and Carl Hasse upon the structure of the vertebral column; and 
there are several clear diagrams to illustrate the conclusions of the 
Breslau Professor, who has succeeded in determining, at least 
generically, the detached fossil vertebre. The Cyclospondyli, Tecto- 
spondyli, and Asterospondyli, of Hasse, are respectively defined, and 
then follows a brief account of the earliest traces of the Selachian 
fishes hitherto discovered, in the form of Onchus, Theicdus, ete. 
The systematic description naturally commences with the primitive 
Notidanidz, and the long-lived Notidanus itself is recorded as the 
only undoubted member of the family as yet recognized; the 
diagram illustrating the dentition of the genus, however, is accident- 
ally overturned, the lower jaw being placed uppermost. It may be 
well also to add that a fossil representative of Chlamydoselache is 
now known from the Pliocene of Italy.’ 
Of the extinct family of Hybodontide, as defined by Zittel, the 
recognized generic types are similarly but few; no well-known 
forms besides Hybodus and Cladodus being regarded as referable to 
this division with certainty. More, however, is known of the type 
genus than the author records; reference might have been made 
to the characters of the shagreen, and especially to Charlesworth * 
and Day’s® determination of the so-called Sphenonchus as a cephalic 
dermal spine of Hybodus. At the present time, also, we are 
acquainted with a portion of the head and vertebral column of a 
closely allied fish from the Chalk.* In fig. 62, the letters a and 6 
are transposed. 
The Cochliodontide follow the Hybodonts, and form an unsatis- 
factory “family,” of which no structural characters beyond those of 
the teeth (except perhaps in Pleurodus) are known. Full references 
are given to the numerous detached teeth named by Agassiz, McCoy, 
St. John, Worthen, Newberry, and James W. Davis; to which is 
added a notice of Traquair’s important discovery of the jaw of 
Psephodus in the Scotch Carboniferous. A new genus, Chaleodus, 
is also founded upon a jaw, having each ramus armed with a single 
thin dental plate, from the Kupferschiefer of Thiiringia. So far as 
external features are concerned, this fossil is very suggestive of the 
teeth of Squaloraja from the Jias, and it would be interesting to 
know to what extent there is an agreement in microscopical structure. 
To the still-surviving Cestraciontide, Orodus, Acrodus, Strophodus, 
and other genera are referred, and excellent illustrative figures are 
given. Owen’s mistake of assigning to Cestracion a side-view of the 
jaws of Myliobatis is, however, repeated (fig. 69). The arrange- 
ment adopted again reminds us of the extreme imperfection of our 
knowledge of the extinct allies of Ceséracion. The true Acrodus 
1 J. W. Davis, Proc. Zool. Soc. 1887, p. 542. 
2 Mag. Nat. Hist. n.s. vol. iv. (1839), p. 245, pl. iv. 
3 Grou. Maa. Vol. II. (1865), p. 565. 
4 Proc. Zool, Soc, 1886, p. 218, pl. xx. 
