106 



G. LINDSTRÖM, HELIOLITID^. 



Fara. Coccoseridae n. 



As a coordinate faioily to the Heliolitidfe and related to it, with some of the species 

 of which it has been coiifouiided, that of the Coccoseridte is to be mentioned. Like the 

 HeliolitidfcB its corallum is composed of calicles with twelve radiate septa, but without any 

 distinct theca, with a more or less abundant coenenchyma, which is corapletely filled 

 with the large erect baculi of which it consists, lying close to each other and only on 

 the surface separated through narrow grooves, which give the false appearance of tubuli. 

 Consequently there are generally no dissepiments in the coenenchyma nor tabulse in the 

 calicles,^ the central part of which is tilled by long tubular rods emerging on the surface 

 as small papillie. A common character for all these is that they have grown in exceedingly 

 thin lamellge, scarcely surpassing a few millimeters in thickness. 



The genera which I think may be placed within this family are three: 



1. Coccoseris Eichwald. 



2. Protarcea E. & H. 



3. Acantholithus n. 



They are all exclusively Lower Silurian. 



Gen. Coccoseris. Eichwald. 

 1860. Eichwald, Lethaea Rossica I, i, p. 442. 



The corallum has grown in thin lamellfe, disciform, with a concentric epitheca; the 

 calicles with broad, triangulär septa, surrounding numerous papilte on the central area. 

 No tabult^. Coenenchyma with narrow, funnelshaped, shallow tubes enclosed by thick 

 compact walls, often papillose or scrobiculate on the edges. For the rest entirely composed 

 of large baculi of the fibrous structure. The species of this genus are geologically distri- 

 buted as indicated in the following table. 



Coccoseris tJngerni Eichwald 



microporus EiCHW. 



megastoma M. CoY 



var. minor . . 



micraster n. . , . 



Lower Silnriau. 



i 



t 



■ 



LeptEena 

 limestone. 



S tv 



o o 





F'- 



J^i 







* 



* 





* 



* 



* 





' Some specimens of Acautholithua make exceptions. 



