K0N6L. SV. VET. AKADEMIENS HANDLINGAE. BAND 32. N:0 I. 79 



the zigzagshaped walls of the tubuli and have a peculiar appearance, placed obliquely 

 above each other f. 22. 



Coenenchymal gem mation has been obsevved in this species as represented in pl. 

 VII, figs. 1, I — IV. It begins from the walls of the tubuli between two aureolas, which 

 are dissolved (ii) in a number of aculaj, surrounded by an irregiilar girdle, the iirsi 

 vestige of the future theca. This (in iii) gains more regularity and the bases of the septa 

 are visible at sevei-al points, while the scattered aculte in the middle show their tops, 

 which at last (iv) are arranged in regular series, the iinal shape being nearly attained: 

 This species comes near to the former, but is well distinguished from it through its 

 coarser and thicker vertical elements, through the larger and more dense septal spines 

 and through the entirely cancellate coenench}iaa with its peculiar intercrossing lamelltB. 



It has been found only in Gotland where it occurs plentifuUy in the uppermost 

 limestone beds, / — A, at the following localities. In the isle of Fårö, from which the name 

 of the species is taken, at Ryssnäs and Dember, at Kylley, Othem, Slite on Lotsbacken, 

 Lännaberget and Enholraen, Tjelders in Boge, Bara backe, Simunde in Bara, Hörsne, 

 Follingbo, Wisby, Myrsjö kanal in Stenkumla, Klinteberg. 



Plasmojjora calycalata. LindstkOm. 



PI. VI, figs. 23—30. 

 1883. Plasmopora calycuhita LiNDSTR. in RiCHTHOFEn's Chiiiii, Bd 4, p. 59, Taf. VII, tigs. 8—9. 



Corallum grown in semiglobular masses with flat base wrinkled by a thin epitheca. 



The calides lie in the midst of the bottom of shallow pits, which are well circum- 

 scribed by a polygonal (commonly pentagonal), ridge. (Pl. vi, fig. 23.) Each sucli well 

 detined cup varies between tive and seven millimeters in diameter. The calicle proper in 

 the midst of it attains 2 millims. This interesting feature of clearly divided areas around 

 the small calicles, more evident in this species than in any other, has given the first 

 impulsion to the interpretation of the nature of the coenenchyma which I have tried to 

 express above (at p. 14, 18). According to this view I consider each such polygonal area 

 as the whole of a calicle proper per se, consisting of the interiör area with the septa, 

 coinmonlj' called the calicle, surrounded by the interiör theca and outside this the exteriör 

 area or börder, commonly called coenenchyma, only separated from the adjacent calicles 

 through the dividing ridge, without any exteriör theca or epitheca. The same characters 

 have been found in other Heliolitidse as stated, through not so pronounced as in this 

 species. What of the coenenchyma in the plurality of the species of this group is con- 

 fluent and not interrupted or marked out by confines and thus forming a common structure 

 for the whole polypary, is in this species portioned of to each individual polyp and thus 

 indicating the signification of its nature. The theca is exsert and raised above the aureola, 

 and in one pieee with the septa. The septa are well developed, straigbt and reach nearly 

 to the centre. The theca forms obtuse angies in face of the septa. They consist of a 



