64 IOWA ACADEMY OF SCIENCES. 



botanist fincls*sometimes on a single tree leaf differences enough for his confusion, 

 these pioneers in Paleophytology have from the dim venation preserved in sand 

 laid a sure foundation for our knov/ledge of the flora of the ancient world. 



In 1878 Lesquereux describect, from what he supposed tertiary beds, (since 

 regarded as belonging to the Laramie group) a single species', and in 1883 he 

 added six luore from the Dakota sandstones; all as heretofore represented by 

 foliar remains except the Laramie specimen, which is described from supposed 

 fossil fruit. In the meantime, however, rather, far before, in 1859, so long ago, the 

 state geologist and chemist of Maryland, Dr. Tyson, had found two Cycad trunks 

 near Coontie station, on the line of the Baltimore & Ohio railway. Dr. Tyson 

 seems not to have appreciated his find. He seems to have referred to the matter 

 in his correspondence, and Rogers, of Pennsylvania, Uhler and others, have pub- 

 lished references to the Maryland Cycads, but for some reason the fossils, strangely 

 enough were never described, never found place in our American geological 

 literature. They lay in the museum of the Baltimore Academy of Science where 

 still they lie, and so neglected were foigotten. We may be sure Lesquereux 

 knew nothing of them, nor Hall, and not until Fontaine in 1889 — thirty 

 years after Tyson first saw the specimens — began the study of the Potomac beds 

 for the United States Geological Survey, did these notable old fossils receive 

 merited recognition and description. In volume XV, Monographs of the United 

 States Geological Survey, Fontaine figures the Maryland Cycads for the first time, 

 and so for science gives them at last " a local habitation and a name." 



Fontaine unable, as he thought, to refer the specimens to any established 

 genus, erected for the Maryland fossil a new genus which, in honor of Dr. Tyson, 

 he called Tymnia, and has thus described it: 



"Trunks varying considerably in shape and size, petrified with silica, more or 

 less flattened; seen with the broader sides in front they are oblongate and trun- 

 cate; in cross-section they arefbroadly sub-elliptical; medulla proportionately small; 

 woody cylinder comparatively thick ; cortical exterior layer with the permanent basis 

 of the petioles very thick; basis of the petioles in cross-section normal sub-rhombic, or 

 sub-triangular with the lower angle very obtuse ; the outer angles acute and prolonged, 

 the superior side forming a curved line bent upwards or forming an obtuse angle, but 

 often from pressure distorted into irregular rhombic or triangular forms; trunks each 

 with a large eccentric terminal leaf-bud, or growing bud; some of the trunks, prob- 

 ably of female plants, have numerous Literal buds; others, probably male plants, 

 are without lateral buds, basis of petioles represented by open casts," etc, 



Mr. Fontaine regards the Maryland forms as constituting a single species — T. 

 marylandka. His new genus, he says, is intermediate between two genera estab- 

 lished by Carruthers, viz. : MantelUa and Bennettites. Garruthers, on being 

 shown a photograph of one of Dr. Tyson's specimens, said: It is obviously a Ben- 

 nettites, and near B. saxbi/atms. It is further to be remarked that Mr. Tyson's 

 specimens are all badly weathered and worn, if we may judge from Tyson's 

 figures. Still the macroscopic characters seem in the main plain enough, but the 

 microscopic characters have never been looked into, at least never published. 



In 1891, in the posthumous volume of Mr. Lesquereux's work,* seven addi- 

 tional species are added to the North American list, as before, all represented by 

 leaf impressions. 



Such was the state of affairs in reference to our North American Cycads down 



1 United States Geol. Survey of the Territories. Vol. VII. 

 ♦Monograph U. S. Geol. Survey, Vol. XVII. 



