Reviews—Dr. W. Dames—The Triassic Ganoids. 459 
IJ.—Tur Grotocy or Lonpon AND oF Part oF THE THAMES VALLEY. 
By Witiram Wuitaker, F.R.S. 
[peace the above title there has just been published a Geological 
Survey Memoir (in two volumes), which gives a very full and 
detailed account of the geology of the district. Vol. i. Descriptive 
Geology, pp. xii. 556, folding table, price 6s.; and vol. ii. Appen- 
dices (well-sections, etc.), pp. iv. 852, price 5s. We hope in a future 
number, after H.M. Government has presented us with a review- 
copy, to give some account of this important work, which, to say 
the least of it, offers a large amount of material for study and for 
reference at an unusually low (official) price. 
Ee, 2Ey) Vie sea Vi = 
Tue Ganorps oF THE German MuscHELKALK. “Dik GANOIDEN 
DES DEUTSCHEN MuscuetKauks.” By Prof. Dr. W. Damss. 
Paleontologische Abhandlungen, Band IV. Heft 2 (1888), pp. 
133-180, pls. xi—xvia. 
O any one accustomed to the writings of Agassiz, Count von 
Minster, H. von Meyer, and others, upon the fossil fish remains 
of the Muschelkalk, Prof. Dames’ memoir will come as a pleasant 
surprise. Instead of a series of scattered teeth and scales, the Pro- 
fessor has brought together from various museums a number of 
valuable specimens affording some real insight into the characters of 
the Mid-Triassic Ganoids ; and the detailed descriptions and discussion 
of these fossils are illustrated by seven fine plates. The specimens 
were almost exclusively obtained from the extra-Alpine Muschelkalk, 
and are referable to the genera Gyrolepis, Agassiz ; Colobodus, 
Agassiz; Crenilepis, Dames; and Serrolepis, Quenstedt. 
The reference of Gyrolepis to the Paleeoniscide is confirmed by 
several fine fossils, and a definition of the genus can at last be 
attempted. The mandibular suspensorium is very oblique, and the 
operculum extremely elongated vertically ; the teeth are long, slender, 
and conical; the dorsal fin is smaller than the anal, and situated 
opposite or in advance of this; there are small fulcra upon each of 
the fins; most of the pectoral fin-rays are not articulated; and the 
two infraclaviculars are fused together. This genus is the only 
Paleoniscid yet described from the European Trias, and Prof. Dames 
recognizes four species, as follows: G. Agassizii (Minster), and G. 
ornatus (Giebel), from the Lower Muschelkalk, G. Albertii, Agassiz, 
from the Upper Muschelkalk, and G. Quenstedti, Dames, from the 
Lettenkohle. 
Gyrolepis Agassizit has until now been assigned either to Ambly- 
pterus or Rhebdolepis; but a comparison of the well-preserved type- 
specimen with more recently discovered examples of Gyrolepis proper 
definitely decides its generic position, and the characters of the scale- 
ornament determine its specific distinctness. G. ornatus has also 
been hitherto referred to Amblypterus, and the type-specimen, now 
figured for the first time, remains unique. G. Alberti is no longer 
