106 Friedrich Dreyer, 



Genus 1: Ommatodiscus, StOhr, 1880, loc. cit, 

 Definition. — Porodiscida without chambered arras and radial 



spines on the margin of the circular or elliptical disk, but 



with one large marginal osculum or opening surrounded by 



a coronet of spines. 



In derselben Weise modifiziert wie die Definition der Sub- 

 familie lautet diese Diagnose: Ommatodisciden mit nur einem 

 Pylom am Rande der runden oder elliptischen resp. ovalen Scheibe. 



Subgenus 1. Ommatodiscinus, Haeckel. 

 Definition. — Disk circular. 



1. Ommatodiscus decipiens, Stohr. 

 Ommatodiscus decipiens, StOhr, 1880, Taf. VI, figs. 8, 8a. 



Disk circular, with two chambered rings around the spherical 

 central chamber, of equal breadth. Chambers twice as high as 

 broad. Pores very small, one-third as broad as the bars between 

 them, two on the breadth of each ring. Osculum of the same 

 breadth as the central chamber, surrounded by numerous very 

 short teeth. 



Dimensions. — Diameter of the disk 0,12; breadth of the 

 central chamber and of each ring 0,03; pores 0,0015. 



Habitat. — Fossil in Tertiary rocks of Sicily, Grotte (StOhr). 



2. Ommatodiscus Stohrii, Haeckel. 



Disk circular, with three chambered rings around the spheri- 

 cal central chamber, of equal breadth. Chambers broader than 

 high. Pores of the same breadth as the bars between them, four 

 on the breadth of each ring. Osculum of the same breadth as 

 the central chamber, surrounded by a corona of ten to twenty 

 thin, bristle-shaped teeth, as long as its diameter. 



Dimensions. — Diameter of the disk 0,2 ; breadth of the cen- 

 tral chamber and of each ring 0,03; pores 0,004. 



Habitat. — North Pacific, Station 244, depth 2900 fathoms. 



3. Ommatodiscus circularis, Haeckel. 



Disk circular, with four circular chambered rings around the 



spherical central chamber of increasing breadth; the fourth ring 



twice as broad as the second. Chambers about as broad as high. 



Pores large, twice as broad as the bars, one to two on the breadth 



