FROM THE SECONDARY ROCKS OF BRITAIN. 11 
altogether unknown ; and that of the third, as far as known, was 
totally different from the supposed structure of Z. macrocephalus. The 
confusion thus introduced was increased by Unger, who added three 
other species in his ■ Genera et Species Plantarum Fossilium,' 1S50, 
npt one of which had, as far as was then known, anything in common 
but its strobiliform shape. Miquel, in his « Prodromus Systematis 
Cycadearum,' 1861, gives all the seven species, adding in a note that 
perhaps some are species of Citpress'uiea, and specially querying Z. 
crassus, the only one in the seven which is probably Cycadean. 
Corda, in Eeuss's 'Die Verstciiierangen der Boimiischen Kreidefor- 
mation,' vol. ii. p. 84 (1846;, carefully examines the affinities ofZamia 
macrocephala. From its structure he concludes that it is certainly not 
a species of Zamia, as the scales are arranged in a different order, and 
the seeds are on the upper surface of the scales, unless, as he suggests, 
the woodcut by Henslow is a mere fiction. He shows that it is totally 
different from Dion, the only recent genus of Cycadea with imbricated 
scales. And he concludes that if it has seeds in pairs on one plane, 
or even a single seed, it may be a Conifer, belonging to a new genus 
allied to Daunnara, if it is not a species of Bammara itself. He thinks 
Eudlicher did well in creating the Cycadean genus Zamiostrobm for it. 
Except that Corda did not observe that Henslow's figure was a dia- 
grammatic restoration, to show his notion of the relation of the seed 
to the scale, and consequently, like Eudlicher, misinterprets it, he has 
from the materials at his command made a very masterly investigation 
of the affinities of this fossil. 
There has been an error in regard to the age as well as to the struc- 
ture of this singular cone, but Mr. Dowker having found his spe- 
cimen in situ, in a pit near Canterbury, has established that it is of 
Tertiary age. 
2. P. ovatns, Car., Geol. Mag. iii. p. 540. Cone ovate, with a trun- 
cate base and obtuse apex; scales with thickened, flat, subquadnm- 
gukir apophyses ; basal scales largest.— Zam ia ovata, Lindl. and Hutt., 
Fossil Flora, vol. iii. p. 189, pi. 826 A. Zamites ovata, Morris, Ann. 
Nat. Hist, 1st series, vol. vii. p. 116. Zamiodrobus ovatus, Gopp., 
I rbers. d. Schles. Ges. 1844, p. 129. 
There is an imperfect specimen of this cone, without the apex, in 
the British Museum, from the Cowderoy collection, which, as far as it 
goes, answers in every respect to that figured by Lindley and liutton. 
