286 BERRY: A NEW MATONIDIUM FROM COLORADO 
depreciate specific differentiation and who, like Professor Seward, 
are more interested in the former distribution of generic types, 
would not hesitate to refer the Colorado form to Matonidium 
Althausit. Such questions are always difficult, and tastes and 
temperaments differ with individual workers. One point of 
view may serve one purpose and the other another. All that need 
be insisted upon in the present connection is that the framing of 
loosely defined specific limits as opposed to finely discriminated 
ones effectually obscures whatever value the fossils may have 
for the elucidation of geologic chronology or problems of the former 
time and avenues of migration, and is a method that has gradually 
become almost obsolete in the allied field of paleozodlogy. 
It would seem a priori incredible that a single botanical species 
should range through the Jurassic and Lower Cretaceous and 
extend over at least two continents in opposite hemispheres; 
nevertheless it is impossible to differentiate the British Jurassic 
from the Wealden forms or these from the still younger Russian 
occurrences, and the specimens referred by Ward to Matonidium 
Althausii from the Albian Fuson formation of the Black Hills* 
in this country cannot be distinguished from the earlier European 
occurrences of that species. 
Recognizing fully the individual variability in Matonidium 
Althausit and the variation in the form and size of the pinnules 
from different parts of a single frond, the Colorado Matonidium 
nevertheless presents a number of apparently constant peculiari- 
ties that serve to mark it as a slightly but consistently different 
type. Among these distinctive features might be mentioned the 
stouter stipe and rachises, the more numerous pinnae, which appear 
to have been at least twice as numerous as in Matonidium Althau- 
sit, judging from the frond bases of the latter as figured by Ettings- 
hausen, Schenk and Seward. The pinnae are more slender in 
the Colorado form and the pinnules are shorter and wider with 
fewer and more nearly circular or isodiametric sori. For example, 
in the form of Matinidium Althausii described from the Black 
Hills the falcate slender pinnules are twice as long as in the Colo- 
rado material, and each bears about twelve pairs of sori. The 
Portuguese specimens as figured by Heer} show eighteen pairs of 
* Ann. Rep. U. S. Geol. Surv. 197: 653. pI. 160, f. 5-8. 1899. 
t Sece. Trab. Geol. Port. 16. pl. 15, f. 1-6. 1881. 


