198 Sellards — Fronds of Crossotheca and Myriotheca. 



dence at hand, whether the entire frond below the apex was 

 fertile, or only a few of its segments. There is no indication 

 of sterile segments below the fertile ones, although some of 

 the incomplete fronds reach a length of 15 or 16°"". It is prob- 

 able that some of the fronds were entirely sterile, and that 

 others were mostly sporangia- bearing, the apical part only 

 being, in most cases, sterile. 



The spores of this species are large, from -056 to -060"™, 

 round, and marked at the apex by three distinct radiating 

 lines. The exospore is thick, resistant, brownish, and marked 

 by minute warty thickenings. 



The sterile fronds were at first doubtfully referred by Les- 

 quereux in the " Coal Flora" to Pecopteris abhreviata Brongn.* 

 In volume iii of the same work, however, a small part of the 

 sterile apex is figured in connection with the fertile frond, and 

 .David White states that Lesquereux's unpublished manuscript 

 contains descriptions and figures of the two parts in connec- 

 tion. f In the Yale collection the fertile and sterile parts are 

 shown in direct connection in no less than nine instances. 

 (See figure 8.) 



Crossotheca trisecta sp. n. 

 Plate VII, figures 4-4c, 9. 



A second and apparently new species is present in the mate- 

 rial from Mazon Creek. The sterile part of the frond is much 

 like that of C. sagittata^ but the fertile pinnules are entirely 

 different. The latter are usually trisectate. The central lobe 

 is ek)ngate-ovate, or nearly round, and borne at the end of a 

 slender stalk. The lateral lobes are smaller, round, and borr^e 

 on short lateral stalks. A second pair is sometimes borne by 

 the larger pinnules. Lateral lobes may be lacking in one or 

 two pinnules near the apex of the pinna. The sporangia are 

 probably smaller than those of C. sagittata^ and are not dis- 

 tinctly preserved on either of the two fertile fronds in the 

 present collection. The sporangia-bearing lobes have a form 

 much like that of the type of the genus C. Crepini^ but the 

 type species lacks the trilobate appearance of the pinnules, 

 and has more finely divided sterile fronds having a different 

 type of venation.:]: C. ophioglossoides from Clinton, Missouri, 

 has narrower and longer fertile pinnules. 



The lines on the upper surface of the pinnule, present on 

 other species of the genus, are much more distinct than on C. 



* Second Geol. Surv. of Penn., Description of the Coal Flora, vol. i, p. 

 248 : Atlas, pi. 46, figs. 4-6, 1880. 



f Mr. White informs the writer that the name Pecopteris Fontainei, sp. 

 nov., is given to the sterile fronds of this species in Lesquereux's manuscript. 



X See the figures of C. Crepini given by Zeiller, Ann. Sci. Nat. (Bot.), ser. 6, 

 vol. xvi, 1883, and by Stur under the name of Soroiheca Crepini, Flora der 

 Schatzlaren Schichten, pi. xxxv, figs. 3, 4. 



