THE MARYLAND CYCADS. 473 



of the former. It is a very distinct species and the only one of the 

 Maryland Potomac species that has the tall subcylindrical form. 



These specimens were collected under the joint operation of the 

 Woman's College and the Maryland Geological Surve,y, and it therefore 

 seems appropriate to name the species in honor of the energetic and 

 efficient head of that survey, Prof. William Bullock Clark. 



PI. LXXXIX, Fig. I, 2, shows the eroded side of the Whitehead 

 trunk, No. 1, M. G. S.-W. C, B., No. 9050, by the side of other trunks. 

 It is fully illustrated on PL CVI. 



PI. LXXXVII, Fig. I, 4, represents the R. T. Donaldson trunk, 

 No. 2, M. G. S.-W. C, B., No. 9052, which is not a trunk at all, but a 

 piece of the upper end of the medulla of some large trunk, and from 

 comparison it might well have l^elonged to the type specimen. No. 9050, 

 found near the same place, but this is not proved. It msij be the whole 

 of the pith of a small conical trunk. It is subconical in shape, sweUing 

 out rapidly near the lower end and hollow within at that part. There 

 is a curious partition across this cavity, dividing it into two unequal 

 parts. It is 20 cm. high, 11 cm. by 17 cm. in diameter at the base, 

 with a girth of 44 cm. Above the swelling the girth is reduced to 36 

 cm. and near the top to 25 cm. It weighs 2.55 kg. (Locality: PL 

 LXXX, No. 106.) 



PL CVI represents the best-preserved side of the Whitehead trunk, 

 No. 1, M. G. S.-W. C, B., No. 9050. It is from a photograph made 

 by the Woman's College. This specimen has furnished all the specific 

 characters known. It represents a large, handsome, barrel-shaped 

 trunk of which all above about the middle is wanting, and the part 

 that remains has suffered much from erosion and decay. The figures 

 show it so fully that special description is scarcely necessary. It has 

 a maximum height of 34 cm. The longer and shorter diameters at 

 the lower fracture are 25 cm. and 13 cm., respectively, and at the upper 

 end 29 cm. and 18 cm. The girth at the corresponding points is 65 cm. 

 and 78 cm. It weighs 17.24 kg. On the two flat sides the erosion 

 reaches the cortical parenchyma and clearly displays the structure 

 caused by the bundles of strands running out into the leaf bases. 

 (Locality: PL LXXX, No. 105.) 



