KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 32, N:0 I. 7 



In the following I have given, first an account of the general structure of the wholc 

 faraily, which being thus ascertained, serves as a basis for secondly to eliminate all those 

 heterogenous fossils, corals and bryozoa, which have for so long tirae been, according to 

 my opinion, wrongly associated with the Heliolitida?. Next I sball give a notice of 

 the geographical and geological distribution. At last these introductory remarks are 

 followed by the detailed descriptions of all genera and species which I have been able to 

 examine. 



In respect to that encumbrance which is called »List of synonyms», I have tried to 

 make it as complete as possible. 1 have, however, excluded -»noinina nuda», or mere cata- 

 logue names, unaccorapanied by descriptions, comments or figures, unless being quite 

 sure of the identity, as for instance in regard to Swedish species, through examina- 

 tion of specimens or by reliable references. Even if an author has identified his 

 specimens with previously decribed species, there is no certainty of the validity of this 

 determination, unless there has been made by him a thorough research of the original 

 specimens. Hence it is necessary to accept a great many synonyms with caution and 

 reserve. 



At last I may be permitted to express m}' deep gi-atitude to the Royal Swedish 

 Academy af Sciences for defraying the expenses of publishing this memoir. I have also 

 to tender my thanks to Herr G. Liljevall, who with the utmost care and with his 

 well known artistic skill has drawn the plurality of the tigures placed on the annexed 

 plates, and given me much valuable assistance in preparing specimens and in clearing 

 up some obscure features of structure. I am, however, afraid that the manner of the 

 reproduction of his drawings is not, at least in some instances, doing full justice to 

 them. 



