310 ANNUAL REPORT SMITHSONIAN INSTITUTION. 1918. 



probably been excessively multiplied, the records show 15 Lower 

 Cretaceous forms. These include Greenland, Spitzbergen, California, 

 and Virginia, and the great display of that time was in western 

 Greenland. 



No less than 25 different species have been recorded from the 

 Upper Cretaceous and the localities include Greenland, Atlantic 

 coast of North America from Marthas Vineyard to Alabama; Kan- 

 sas, Colorado, Wyoming, and British Columbia in the west; Bo- 

 hemia, Moravia, Saxony, Rhenish Prussia, and Bulgaria in Europe; 

 and New Zealand, Sachalin Island on the east coast of Asia. Glei- 

 chenia becomes much less abundant in the Tertiary and all of the 

 known Tertiary records are pre-Miocene. Four species are known — 

 two Oligocene species in Saxony, an Eocene or Oligocene species in 

 Nevada, and a middle Eocene species in the south of England. 



The family Matoniaceae with but two existing species of Borneo 

 and the Malay Peninsula was prominent in older Mesozoic floras 

 from the Upper Triassic through the Jurassic, at which time it was 

 represented by a variety of widespread species referred to the genera 

 Laccopteris and Matonidium. Still more interesting is the family 

 Dipteriaceae with the single existing genus, Dipteris, with but four 

 species confined to the Malayasian region and found growing in 

 association with Matonia. 



The Dipteriaceae became dominant slightly earlier than the Ma- 

 toniaceae, and the magnificent lyrate fronds of some of the species 

 are exceedingly common in the Triassic, at which time the genera 

 Dictyophyllum, Clathropteris, Thaumatopteris, and Camptopteris 

 are represented. They had lyre-shaped fronds of large size, consist- 

 ing of many separate or slightly united, serrate margined, and netted 

 veined pinnules, arranged digitately on a forking stipe; and annulate 

 sporangia much like the existing Dipteris. The striking appearance 

 of these forms is better illustrated by the accompanying restorations 

 than they would be by any amount of descriptive text. Clathropteris 

 and Dictyophyllum survived into the succeeding Jurassic, where they 

 were on the wane, becoming replaced in the Cretaceous by forms more 

 like the modern Dipteris and referred to the genus Protorhipis 

 (Hausmannia). The sketch map (fig. 5) shows the cosmopolitanism 

 of the family in the Mesozoic and the restricted distribution of the 

 few existing species. Restorations are shown in figs. 32-34. 



The family Hymenophyllaceae, comprising the existing filmy 

 ferns, is practically unknown in the fossil record although several 

 Paleozoic genera (Hymenophyllites, Rhodea, Acrocarpus) have been 

 referred to it upon insufficient grounds. 



Without mentioning the various small modern families unknown 

 in the fossil state, there remains the two families Cyathaceae and 

 Polypodiaceae. The former are almost exclusively tree ferns in the 



