ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
49 
itself a combination of two heterogeneous sets of plates — the ambulacral, 
which are binary from the beginning, and the secondary perisomatic 
interradia, which commence singly and then become binary. 
The origin and history of the buccal membrane is thus described ; 
the massive teeth and jaws “ in the act of forming require an abundant 
supply of organized calcareous substance, and in the future imago they 
will demand, powerful instruments as they are of prehension and dimi- 
nution, the greatest possible facility of motion. For their sake, it will 
seem to me, in order to prepare for them pliant surroundings, the 
currents of development are at last turned, and calcareous matter, just 
deposited in duly formed skeletal constituents, is reabsorbed, remodelling 
in the Cidaridae and Echinothuriidte, all but dissolving in the other 
groups.” 
The structure of the dental apparatus is considered in great detail, 
and it is suggested that further researches will tend to show that of the 
tooth-bearing Echinoids the Regularia are predacious, and perhaps mainly 
carnivorous animals, while the Irregularia are rather omnivorous. 
We have been able to draw attention to some only of the points of 
interest in this memoir. 
Catalogue of British Echinoderms.* — Prof. F. Jeffrey Bell has 
prepared a catalogue of the British Echinoderms in the collection of the 
British Museum (Natural History). The term British area is recognized 
as denoting an artificial region, and that accepted extends from the 
Faeroe Channel to the Channel Islands, while all forms are included 
which do not belong to essentially abyssal groups, such as Elasipods or 
Stalked Crinoids. One hundred and thirty-two species, some of which 
are very imperfectly known, are enumerated, compared with the fifty- 
five of Forbes’s well-known works, but eight of these latter are not now 
regarded as good species. 
After an introduction, in which there is given a sketch of Echino- 
derms and of their development, an account is given of the classification 
of the higher groups, in which the arrangement proposed by the author 
in 1891 is followed. The special part deals first with a description of 
the genera and species, to both of which “ keys ” are given by which a 
collected specimen may be quickly hunted down to his proper place ; 
the diagnoses are drawn up as briefly as possible, and from what is said 
in the introduction it is clear that Prof. Bell has a holy horror of any- 
thing like verbosity or padding. 
The last part of the work is occupied by an account of the distri- 
bution of the species, arranged in five tables. The first gives an account 
of the horizontal distribution of British Echinoderma beyond the 
“ British Area,” and in the same line the range in depth of each species 
is noted. Twenty-four species are not known beyond this artificial 
area, and these are (1) littoral and rare or very local, of which there are 
only three, (2) incompletely known — five, and (3) deep-water forms ; 
many of the sixteen of these last are known from single specimens or 
have been only lately described. Only one species is not known beyond 
ten fathoms, whereas twenty-four have been dredged from more than 
* ‘Catalogue of the British Echinoderms in the British Museum (Natural 
History), by F. Jeffrey Bell, M.A. London, printed by order of the Trustees,’ 
1892, 8vo, xv. and 202 pp., 16 plates (2 colrd.) and 5 woodcuts. 
1893. 
E 
