XXl] DIPTERIDINAE 385 



D. Natharsti. No sporangia have been found on English 

 specimens, but it is safe to assume their agreement with, those 

 of other species. A more complete list of records of D. rugosum 

 is given in the first volume of the British Museum Catalogue 

 of Jurassic plants ^ 



Nathorst^ has recently drawn attention to certain differences 

 between Dictyophyllum and Dipteris. The pinnate division of 

 the pinnae is not represented in the fronds of the recent species, 

 but this method of lobing, which is a marked characteristic of 

 Dictyophyllum, is less prominent in Clathropteris; and in Gamp- 

 topteris lumensis Stur^, an Austrian Upper Triassic species, the 

 pinnae are entire. In Dictyophyllum the sori cover the whole 

 lower surface of the leaf; in Dipteris they are more widely 

 separated and the sporangia have a diameter of 0"02 mm., but 

 in Dictyophyllum the diameter is 0*4 — 0"6 mm. Moreover in 

 Dictyophyllum the sori contain 5 to 8 sporangia, whereas in 

 .Dipteris they are much more numerous. Despite these dif- 

 ferences it is clear, as Nathorst says, that Dictyophyllum, 

 Clathropteris, and Gamptopteris are existing types very closely 

 allied to Dipteris. It is a matter of secondary importance 

 whether we include all in the Dipteridinae or follow Nathorst's 

 suggestion and refer the fossil genera to the separate family 

 Camptopteridinae. 



Thau matopteris. 



This genus, founded by Goeppert* for a Rhaetic plant 

 from Bayreuth, is by some authors ° regarded as identical 

 with Dictyophyllum, but it has recently been resuscitated by 

 Nathorst® for specimens which he names T. Schenki, formerly 

 included by Schenk in his species T. Brawniana''. It bears 

 a close resemblance, in the long linear pinnules with an entire 

 or crenulate margin, to Dictyophyllum Fuchsi described by 

 Zeiller^ from Tonkin, and it would seem hardly necessary to 

 adopt a distinctive generic designation. The sporangia have 



1 Seward (00) p. 122. ^ Nathorst (06=). 



3 Krasser (09) p. HI. * Goeppert (41). 



5 Seward and Dale (01) p. 503. ^ Nathorst (07'''). 



7 Schenk (67) A. PI. xviii. » Zeiller (03). 



