340 
NATURE 
[AucusT 7, 1902 
Mr. Boulenger. Already a lavishly illustrated quarto 
volume (‘‘ Annales du Musée du Congo”) had been issued 
containing descriptions and figures, by the same author, 
of new genera and species of fishes recently discovered in 
the Congo, and now comes the present work, the twenty- 
five plates of which are “half-tone” reproductions of the 
lithographs illustrating the descriptions in the “ Annales.” 
This is the first work dealing with a group of animals 
over the whole extent of the Congo Basin, z.e. including 
Lake Tanganyika. It commences with an introduction 
divided into six parts, namely, (1) general characters of 
the fresh-water fishes of Africa, (2) distribution of fishes 
in the Congo Basin, (3) fisheries and methods of capture, 
(4) methods of preservation and transport of fishes for 
scientific purposes, (5) terminology used in scientific 
descriptions of fishes, (6) list of previous writings 
specially dealing with the fishes of the Congo Basin. 
A few years ago, about 9o species of fishes were known 
from the Congo Basin, but in the present work the list 
is swelled to no less than 320, 78 of which are confined 
to Lake Tanganyika. The families most abundantly 
represented are Mormyrida, Characinide, Siluridz and 
Cichlid, the name for the last-mentioned family being 
for good reasons adopted in place of the better-known 
“ Chromidz.” 
I am glad to see that, in spite of Cope’s dictum, Mr. 
Boulenger still considers the Lampreys to be “fishes,” 
as he divides the class into three subclasses—Cyclostomi, 
Chondropterygii and Teleostomi. Only the last is repre- 
sented in the fish-fauna of the Congo Basin. 
The Teleostomi include here the Crossopterygii, the 
Dipneusti (the usual name “ Dipnoi” is rejected on 
account of its having been originally used to designate 
the Batrachia) and the Teleostei. Our author seems 
inclined to retain the “ Ganoids” (= Acipenseroidei and 
Lepidosteoidei) as a distinct order, but as none of these 
inhabit the basin of the Congo, the question is not gone 
into ina detailed manner. As to the Crossopterygii, Mr. 
Boulenger admits only two primary divisions, the extinct 
Osteolepida and the modern Cladistia, represented in 
African rivers by the singular though well-known family 
Polypteridz, of which five species of Polypterus, three 
being new additions, and one of Calamichthys are here 
chronicled. As regards the Dipneusti, in the course of 
some interesting remarks on vertebrate limb theories, 
the author adopts Dollo’s view as to their probable de- 
rivation from the Crossopterygii, the corollary to which, 
as the present writer has also pointed out, is that the 
“archipterygial” form of limb must have been diphy- 
letically realised, on the one hand, by the Pleuracanthid 
Selachii, and on the other by the Holoptychii and the 
lung-fishes. An interesting new species of Protopterus 
(P. Dolloz) is here described and figured. 
Proceeding to the ordinary bony fishes or “‘ Teleostei,” 
we may note in the first suborder, that of the Malaco- 
pterygii, the extraordinary variety of form among the 
Mormyride, even within the limits of one genus, as in 
the case of Mormyrops curtus and M. attenuatus (plate iii). 
Sagemahl is followed in the association of the four 
families of Characinide, Cyprinidz, Siluridee and Gym- 
notidz in one group or suborder of Ostariophysi, the 
essential characteristic of which is the presence of the 
Weberian ossicles, by which the swim bladder is brought 
NO. I710, VOL. 66] 
4 
into relation with the ear. The Cyprinodonts, of which 
the region produces four species all belonging to the 
genus Haplochilus, are included with the Esocide, 
Dalliidee and Amblyopside ina third suborder, that of 
the Haplomi. A fourth is formed by the Percesoces 
(the Miillerian “ Pharyngognathi” being entirely aban- 
doned), and which includes, not merely the Scomber- 
esocidze, but also the Ammodytide, Atherinidz, Mugilidz, 
Polynemidze, Sphyrzenidze, Ophiocephalidee and Anaban- 
tidz. Coming now to the fifth suborder of Teleostei, 
that of the Acanthopterygii, we find that, with the excep- 
tion of a few Serranid:e, Scizenidee and Pristipomatide, 
it is entirely represented by twenty-four genera and 
eighty-seven species of one family, that of the Cichlidz 
(= Chromidze of Giinther). This family, which was also 
included in the “ Pharyngognathi” of the Miillerian 
system, is here considered as closely allied to the Perches, 
in spite of the fusion of the inferior pharyngeal bones. 
The diversity of genera of this family in Lake Tangan- 
yika is worthy of notice. The volume finishes with a 
description of eleven species of Mastacembelus (sub- 
order Opisthomi) and one of Tetrodon (suborder 
Plectognathi). 
In conclusion, it may be said that the talented author 
is to be congratulated on the interesting work he has 
produced, and the zoological public in having, in so com- 
pact a form,a guide to a general knowledge of the fresh- 
water fish-fauna of so large a portion of the African 
continent, interspersed with many valuable remarks 
bearing on the subject from a morphological as well as 
systematic standpoint. Rey blade 
APPLIED MECHANICS. 
The Roorkee Manual of Applied Mechanics, Stability 
of Structures, and the Graphic Determination of Lines 
of Resistance. Vol. ii. By Lieut.-Colonel J. H. C. 
Harrison, C.E., late Assistant Principal, Thomason 
Civil Engineering College, Roorkee. Pp. vili+318 
+70. (Roorkee: Printed at Thomason Civil Engin- 
eering College Press.) 
HIS “ Manual of Applied Mechanics” is primarily 
intended for the use of students of the Thomason 
Civil Engineering College, Roorkee, North-West Pro- 
vinces, India. It forms an extension of vol. i.; the 
latter was originally prepared by Lieut.-Colonel A. 
Cunningham, R.E., and was revised by the present 
author in 1895. 
Vol. i. does not include important subjects such as the 
stability of block-work, the design of retaining walls, 
abutments, masonry arches, earthwork, foundations, &c. 
These omissions have been met by the issue of vol. ii. 
Moreover, the treatment in vol. i. is mainly analytical, 
whereas in vol. ii. graphical methods have been deve- 
loped and largely employed; so that the two volumes 
together now form a very complete treatise on the prin- 
ciples of mechanics as applied to roofs, girders, bridges, 
foundations and allied structures. 
In the first part of the volume under review the author 
describes the plotting of vector and link polygons for a 
general system of forces inone plane. Then, in reference 
to various types of structures, suchas beams, cantilevers, 
block-work, suspension chains, and arches he develops 
