Maryland Geological Survey 383 



Thyrsopteris microloba alata Fontaine, 1906, in Ward, Mon. U. S. Geo I. 



Surv., vol. xlviii, 1905, p. 281. 

 Thyrsopteris elliptica Knowlton, 1907, Smith. Misc. Coll., vol. iv, pt. i, 



p. 110. 

 Onychiopsis Ooepperti Berry, 1911, Proc. U. S. Natl. Mus., vol. xli, p. 325. 



Description. — "Frond slender, bi-tri pinnated; sterile pinnae alternate 

 or rarely opposite, elongated, their length rapidly increasing towards 

 the lower part of the frond ; pinnules alternate, acutely directed forward, 

 lanceolate or linearly-lanceolate, entire or lobed, or even pinnately 

 parted; lobes or partitions acute at apex and acutely directed forward 

 just like the pinnules themselves. Venation obsolete, secondary veins 

 simple, each going into a lobe. Fertile pinnules elongated, with a linear 

 terminal sorus on both sides of the midrib." — Yokoyama, 1890. 



A very large number of Fontaine's species of Tliyrsopteris fall within 

 the limits of this species. There is, to be sure, some variation in the 

 relative length and breadth of the pinnules, but the material shows every 

 gradation of form, it being possible to select individual pinnules from a 

 single frond fragment which exemplify several of the supposed types. 

 On the whole, the pinnules are somewhat more robust than in the foreign 

 material, and the rachis is inclined to be stouter and may or may not 

 be winged. 



This is an exceedingly common form in the Potomac from the oldest 

 to the youngest stratum, and it has also been recorded from the Kootanie 

 of Montana at Great Falls, Geyser, etc., and possibly some of Dawson's 

 identifications of Asplenium. Dicksonianum Heer from the Canadian 

 Kootanie should also be referred to this species. It also occurs in the 

 Lakota formation of the Black Hills. Abroad it is rather rare in the 

 English and German Wealden, but its geological distribution in the 

 Lower Cretaceous of Portugal rivals that of eastern America, since it 

 comprises considerable material from the Valanginian, Barremian, and 

 Albian terranes. With regard to its occurrence in the Neocomian of 

 eastern Asia, Yokoyama writes {loc. cit.) that it is the " chief and char- 

 acteristic fossil of the Japanese flora, being found in all of the fossil 

 localities." 



That this species or Onychiopsis psilotoides, or both, occur in the 

 Kome beds of western Greenland seems probable, and several of Heer's 



