236 Reviews—Gerhard Holm on the Genus Illenus. 
rocks, and the formation of limestones, the general remarks on the 
deposition of the strata, and their relations to other groups in various 
parts of Europe, the full lists of fossils, and above all the descriptions 
of new species of organic remains belonging to so many different classes, 
indicate a range of knowledge that very few dare essay to attain. 
H. B. W. 
V.—Der Svenska arterna AF Tritoprastierer Innmnus (Daman). 
Af Grruarp Horm. Med sex Taflor. Bihang till K. Svenska 
Vet. Akad. Handlingar, Band 7, No. 3. (Stockholm: Norstedt 
& Soner, 1882.) 
Tue SwepisH SpEcrEs oF THE Genus Jtta@nus (Datman). By Grruarp 
Horm. Supplement to the Proceedings of the Royal Swedish 
Academy, Vol. 7, No. 3. 8vo. pp. 148. With 6 Plates. 
HIS memoir covers wider ground than is implied in its title; for, 
besides a minute deseription of all the Trilobites belonging to this 
genus which are found in Swedish strata, it also contains a general 
history of the genus, and of all the known species placed under it, 
with references to the works in which they have been described and 
the strata and country where found, and also the known portions of 
the body of each species; so that in a sense it may be regarded as 
a condensed monograph of the genus.. 
The author follows Barrande in placing the genus under two sub- 
divisions: (1) Z//enws in the striet sense of Dalman, and (2) Bumastes, 
Murchison. Salter split this genus into eight sub-genera, partly 
according to the number of the body-segments; but with the exception 
of Bumastes and Illenopsis (probably a quite distinct genus) Dr. Holm 
rejects Salter’s divisions. 
To all workers in Ordovian strata the general features of the genus 
are well known. The body is oval or elliptic, strongly convex, the 
head and pygidium are about the same size, the thoracic segments vary 
from 8 to 10 in number, eyes are mostly present, though some species 
are destitute of them. The genus has its greatest development in the 
Ordovian period, it passes up to the Silurian proper, but not beyond. 
The author catalogues no fewer than 100 species; of which 85 belong 
to Lilanus proper, and 15 to Bumastes. In North America 35 species 
are known, in Sweden 19, Great Britain 17, Bohemia 17, Russia 15, 
Norway 4, Spain and Portugal 3, France 2, Asia (Himalaya) 2, 
Bavaria 1, Australia 1. 
Of the 19 Swedish species, 10 are here described as new; they 
make their first appearance in that country in the Orthoceras-kalk ; 
then in the Chasmops-kalk, where they are most numerous; Trinucleus 
shales, the Brachiopoda shales with a single species, the Lepteena-kalk, 
and finally in the Silurian proper (ofver-silur), with two species of 
Bumastes. 
Though written in Swedish, the generic and specific characters are 
also given in Latin. The new species, as well as some previously 
known, are figured. Gi. de 
