176 Scientijie Intelligence. 



Dakota ; an exhaustive description of the occurrence and macro- 

 scopic characters of the cycadeoidean trunks from the lower 

 members of the Potomac group of Maryland, illustrated by many 

 plates ; the description of various additional plants or specimens 

 from the Potomac group of both Virginia and Maryland with 

 various correlations and a discussion of the age of the beds. 



The study of the Maryland and Wyoming cycadean trunks is 

 by Professor Ward. The most of the descriptions of flora? are 

 by Professor Fontaine. Mr. Bibbins contributes a paper on the 

 Potomac group and the occurrence of the cycadean trunks 

 therein, together with a splendid triple-plate map (Plate LXXX), 

 showing the areal distribution of the formations of the Potomac 

 group in Maryland, on which are indicated all of the known 

 plant and cycadean trunk localities. Mr. Wieland's contribu- 

 tions to the volume include the discovery of the leaves of the 

 Wyoming cycad trunks, with some account of their structure, 

 and tAvo papers on the stratigraphy and paleontology of the 

 Black Hills rim, including a description of the leaves of the 

 Lakotan quasi-cycad JSfilssonia nigricollensis, strikingly like some 

 of the forms of the Oregon Jurassic described by Fontaine. 



Most interesting is the beautiful cycadean trunk from the 

 Grapevine Valley of Colusa County, California, described by 

 Professor Ward. This fossil is from the lower Chico or Horse- 

 town beds, the strata in which it occurs doubtless being of much 

 the same age as those yielding the numerous cycadean trunks in 

 Maryland and South Dakota. The most interesting feature dis- 

 played by the trunk is the presence of a peduncle in the axil of 

 every leaf -base of the lateral trunk surface. This extraordinarily 

 prolific growth of axillary fruits likewise characterizes the fine 

 type Cycadeoidea nigra from Boulder, Colorado, but is not found 

 in equal degree in any other cycadean specimens. 



For the first time the Cycad trunks from Maryland are 

 adequately illustrated by numerous and beautiful plates, and Pro- 

 fessor Ward also adds many views of additional trunks and 

 finely conserved fragments from the Freezout Hills of Wyo- 

 ming. While holding the illustration and descriptions given by 

 Professor Ward as in the main most effective, necessary and 

 admirable, the reviewer nevertheless feels called upon to say that 

 he does not find from his own anatomical and structural studies 

 that there is any such great specific variation as is ascribed to 

 these cycads. Macroscopic leaf-base and armor characters may 

 serve to distinguish certain occasional and unique specimens 

 within specific limits ; but as soon as one comes to deal with a 

 large number of trunks, so many transitions in preservation and 

 structure appear that the method fails of accuracy. 



The study of the additional materials from the Potomac series 

 of Virginia and Maryland shows a similarity of floral change in 

 these beds of both states. It also appears that while impor- 

 tant floral changes of the Potomac group are evident in the 

 Paritan, little change in vegetation occurred during the Patuxent 



