318 Reviews—Dr. Traquair on the Platysomida. 
thinks it may facilitate an explanation of the mode of formation of 
manganese deposits, as they occur in connexion with the diaspro 
rich in fossils, and hints, that it would make us doubt the possibility 
of their being formed by an endogenous action, or from deposits of 
mineral water. . 
Prof. de Stefani called attention to the use the microscope may 
now be to the anthropologists, in showing from what locality imple- 
ments made of this rock were derived. 
The writer of this notice believes he is in a position to refer to the 
Eocene “diaspro” the rock mentioned by Prof. Bonney in this 
Magazine last year (August, No. 182, p. 369), in which attention 
was called to its containing fossils, which Prof. Bonney was himself 
inclined to refer to Radiolaria and Bryozoa, and ean also add that 
Professor Pantanelli has in the press an article describing a large 
number of the Radiolaria observed. 
TEES Vie iii 
HSE 
J.—On tue Structure anp AFFINITIES OF THE Piarysomipm. By 
Ramsay H. Traqguarr, M.D. Transactions of the Royal Society 
of Edinburgh, vol. xxix. pp. 348-391, Pls. ii.-vi._ 
N the above memoir Dr. Traquair discusses an interesting group 
of deep-bodied Paleozoic fishes, some forms of which haye 
long perplexed Palzichthyologists as regards their affinities and 
systematic position among the Ganoids. The position and form 
of the teeth, the skeletal structure, conformation and attachment of 
the scales; the absence, presence, or form of certain fins, having 
been the objects respectively studied, has led, as a natural conse- 
quence, to the publication of many and diverse opinions in regard to 
these characters, and their bearing upon the classification. Yet none 
of the respective authors have hitherto succeeded in establishing the 
natural position of the group in the above order of fishes upon a 
basis sufficiently satisfactory to be permanently, or even generally 
accepted; nor has their relationship to the many, and in some instances 
widely separated genera, with which they have been associated by 
one author or the other. 
In a concise but comprehensive introduction, which commences 
with an enumeration of the genera Dr. Traquair refers to the family 
Platysomide as enlarged by himself (viz. Hurynotus, Ag.; Bene- 
denius, Traq.; Desolepis, Young ; Eurysomus; Young; Wardichthys,. 
Traq.; Cheirodus, M‘Coy (Amphicentrum, Young); Platysomus, Ag.), 
is embodied the various views enunciated respecting the structure 
and classification of some of these genera, of which tke following is 
a brief resumé. Agassiz classed Eurynotus and Platysomus (including 
Eurysomus) in his Lepidoid family of Ganoids. | Giebel includes the 
same genera in his “‘ Heterocerci Monopterygii,” along with Paleo- 
niscoid genera, and also with Augnathus, Conodus, and Megalichthys. 
Quenstedt places Platysomus among the Heterocercal Ganoids, 
immediately after Palcwoniscus, Amblypterus, and Pygopterus. Sir 
Philip Egerton advocated the removal of Platysomus to the Pycno- 
