404 .ions. HOYi: pi:ti:i?si:n 



I have |)reviously 1924 III. p. 17) lind occasioii lo poiiil oiil ihat 

 Clcvo s »lia{»nosis of tiiis species is crroneous i^Syn II. p. 80), whereas 

 Lagers ti'd t' s original (lescripliDii lits the case vcry well. Possibly it 

 was ('Jevc's (lesciiplion Ihat led Ilustedt astray, so that lic iisod tlie 

 naiiie in 'Dio Macillariaccen Vegetation des .Sarekj^ebir^es- li)24 aboiit 

 a form thai is (piile dislincl liom the present form and evidently belongs 

 to Ihe forms ccntrinj^ roiind P. /huvu. 



Like most of the I'iiiniilarid species, P. intirmedia shows considerable 

 variation in the shape and size of the valve, as also in the closeness 

 and direclion of the striation. There are, however. several characteri- 

 stics which recur more or Icss distinclly in all the forms: 



1. The striæ comc extremely close lo the raphe. 



2. The stricv nearest to the transapical fascia are not shortened ^^see, 

 however. Lagerstedt 1873, Taf. I, fig. 3a\ 



3. The striæ are radiale in the middle and converge at the apices. 

 In very shorl forms they are occasionally almost parallel. 



4. In the larger forms the striæ are broader near the raphe than at 

 the margin of the valve. In smaller forms this is less pronounced 

 but is often seen cpiite distinctly. 



5. In all the forms mcntioned behnv there will occur specimens that 

 are slightlv constricted in the middle. 



'r>' 



in Ihc Icelundic niaterial I have Ijcen ablc to distinguish betvveen 

 the following forms, between which intermediate forms often occur, 

 especially within the two groups into which I have divided them. 



A. Smaller forms. 



f. 1. Valve oblong-elliptical with rounded ajiices. L. 22 — 26//, br. 4,5 — 

 5,1- //, sir. 12 in 10//. Fig. 24 a. 



f. 2. \'alve elli|)tical with rounded or slightly cuneate apices. The 

 striæ are frecpientiv almost parallel. L. 13— 15//, br. 4,6— 5,5//. str. abt. 9. 

 Fig. 24 b, c. 



f. 3. Valve linear, with broad. truncate. somewhat produced capitate 

 apices, more or less constricted in the middle. L. 24 //. br. 5,y //. str. 9 — 

 10. (Boye P. 1915. p. 293, fig. 19 belongs lo this form). Fig. 24d. 



H. Larger forms. 



f. 4. Valve linear, constricted in the middle with a slight gibbosity 

 here. so that tlic valve becomes slightly triundulate; apices cuneate- 

 truncate or rounded. L. 33 //, br. 7,u //, str. 8,2 in 10//. Fig. 24e. 



f. 5. Valve linear, with rounded apices. L. 24//, br, 6.6 //, str. abt. 8 

 in 10// Lagerstedt 1873. Taf, I, fig. Sa^). Fig. 24 f. 



C. .Somewhat doubtful form. 



f. 6. Valve linear, somewhat constricted in the middle. with jiointed 

 cuneate a|)ices. L. 22//, br. 5,5//, str. abt. 12 in 10//. Seems to sliow 

 most aflinity to f. 1. Fig. 24 g. 



These forms were distributed as follows: 



f. 1. E. Icel 7. L. 4(1. (i!), 77. 113, L. 129 — N. Icel. 160, 162. L. 179, 182, 

 L. 184, 217. 219. L. 241. L. 253 — N. W. Icel. L. 268 — W. Icel. 

 L. 307 - S. Icel L. 295, L. 353. 



