Swedish Cambiran-Siberian H. and C. 438 
SWEDISH CAMBRIAN-SIBERIAN HYOLITHIDAD AND 
CONULARIID.Az.' 
This memoir marks an era in the study of these conical shells 
of the older Palceozoic rocks. The author, Dr. Gerard Holm }.as had 
unusual facilities for the examination of these fossils, having had 
before him the large collections of the Swedish Geological Survey, 
amounting to over 1100 examples, and 45 opercule, as well as 
numerous specimens from the museums of Stockholm, Upsala, 
Christiania, Copenhagen, &e. 
Dr. Holm discus-es the zoological position of Hyolithes at con- 
siderable length, of which the following is a summary : 
This type of shell was at first taken to be a Pteropod, and has 
been so described in all the earlier, and best known works on Pals- 
ontology, but of late years serious objections have been made to 
this view. 
Among the objectors are Neumayr and Pelseneer; the former of 
these writer: (1879-89) considers that the Hyolithide belong te an 
entirely independent extinct group of animals, which never had a 
place near the Pteropods, but were nearly related to the Gasteropods ; 
he thinks there can be scarcely any doubt that they are molluscs. 
Neumayr undoubtedly makes a mistake when he, following the 
old custom, unites the genera Hyolithus and Conularia in the one 
family or division. Between these genera there are surely great 
differences—as the following : 
In Hyolithes the shell is solid, rigid, thick, and consists of at 
least three layers; it is composed of calcium-carbonate. In Conu- 
laria it is thin, flexible, and formed of calcium-phosphate, united 
with a horny substance. 
In Hyolithes the shell is bilaterally symmetrical with dorsal and 
ventral sides plainly marked. Inu Conularia it is quadrately or 
trhomb'cally prismatic, without any distinct dorsal and ventral 
side, etc. 
The mouth of the shell in Hyolithes is not drawn together, but is 
always furnishea with an operculum. In Conularia, on the con- 
trary, the mouth has its four sides bentinward, and never has an 
operculum. 
Hyolithes appeared earlier than Conularia, and there is no indica- 
tion that the latter spring from any form of the former, or from 
any common ancestor. 
Lindstr6m has examined the zoological standing of Conulariidz 
and concludes that they ought to be referred permanently to the 
1Sveriges Kambrisk—Siluriska Hyolithide och Connlarindes, Series C., No. 
112 af Gerhard Holm, Stockholm, 1893. 
