Sellards — Fronds of Crossotheca and Myriotheca. 199 



sagittata^ and sometimes branch. The figured specimen is 

 15^"" long ; the first 5 or Q'^^ are sterile, the remaining pinnae 

 being partly or entirely fertile. When detached and in fragments 

 the sterile part of the frond is distinguished with difficulty 

 from that of C. sagittata. The pinnules are perhaps more 

 finely lobate. 



The spores are smaller than those of C. sagittata, measuring 

 from -030 to •036°'™. They are somewhat triangular, with a 

 smooth, thin exospore. 



The name Crossotheca trisecta is suggested for the species. 



Myriotheca. 

 Zeiller, Ann. Sci. Nat. (Bot.), ser. 6, vol. xvi, 1883. 



Myriotheca has numerous independent, sessile, round or 

 egg-shaped sporangia, covering the entire lower surface of the 

 pinnule. The genus is represented at Mazon Creek by a single 

 species, which apparently is the fern described by Lesquereux 

 from Morris, 111., as Sphenopteris scaberrhna,^ although the 

 rachis is smooth or striate, not punctate as given for that 

 species. The round sporangia are very numerous, close, or 

 almost contiguous, half immersed in the leaf substance, and 

 cover the entire lower surface without any kind of regularity 

 of arrangement or grouping. The spores are of medium size, 

 measuring from -036 to •04:0"'™, triangular, with the sides some- 

 times slightly concave. The genus is a rare one both in 

 Europe and in America. No other species has been reported 

 from this country. The genus was founded by Zeiller on a 

 single fragment from the Coal Measures of France. The 

 European specimen representing the type species, 3L Desaillyi, 

 has smaller pinnules with a tendency to become lobate. The 

 sporangia of the American species are nearly round, and larger 

 than those of the European species, measuring 'ttO to '50™™. 



Because of the absence of any indication of an annulus. Prof. 

 Zeiller included both Crossotheca and Myriotheca with the 

 Marattiacese. The large size of the spores and comparatively 

 small output to the sporangium are, however, characters not 

 met with in the living representatives of that group. The 

 position of the sporangia, marginal in Crossotheca, and cover- 

 ing the whole lower surface of Myriotheca, is unusual for 

 Marattiaceous ferns. 



Spores of other Ferns from the same Locality. 



At least four other species of ferns in the Yale collection 

 have the spores preserved. All retain their natural brown 

 color, and something of their food contents, and, as far as 

 appearances are concerned, might be spores from living plants. 



* Geol. Surv. of Illinois, vol. iv, p. 408, pi. sv, figs. 1 and 2, 1870. 



