G. R. Wieland — Williamsonian Tribe. 



451 



localities of Mesozoic fossil cycads indicated on the map, fig. 

 1, have so far failed to yield other than scattered fruits. In 

 truth it has required not only the renewed field work on the 

 Yorkshire coast, but the rickesse of Williamsonian fruits in the 

 newly discovered Mexican horizons to fully and finally dispel 

 this mistaken idea of the rarity of casts, imprints and fruits, 

 and especially of difficulty in learning the import of the main 

 facts of association. These fossils doubtless occur in most 

 of the localities yielding fronds; their fragile nature, with 

 occurrence in clays and shales barren of economic products 

 save occasional scant seams of coal, are amongst the obvious 



Fig. 9. 



Fig. 9. Williamsonia gigas. x 1/3. Slab containing foliage and two 

 fructifications weathered out in nearly full relief. That to the right is an 

 ovulate fruit of the largest size. (Yale — James Yates Collection.) 



reasons for infrequency of observation or collection. Though 

 it is of interest to observe in this connection that aside from 

 silicified fruits, casts of singular beauty are confined neither to 

 the Williamsonise nor to the Mesozoic. When I was in Paris 

 a few years since, Professor Zeiller showed me the original 

 type of his Lepidostrobus Laurent), (18), a cast broken out of 

 certain Dinantien phosphatic nodules from the flanks of the 

 Pyrenees. Uncrushed, and without any adherent matrix, the 

 original form and larger features, including the sporangial 

 outlines, all appear so much as in life that both illustration and 

 description fail to visualize the singular beauty of this fossil. 



The lack of earlier attention to the fuller possibilities of the 

 Yorkshire coast is now, however, not alone compensated for 



-Fourth Series, Vol. XXXII, No. 192.— December, 1911. 



Am. Jour. 



Sci.- 

 33 



