Dr. Engelmann on the Cereus giganteus of California, 231 
gons below are twice as distant; each set in turn may be seen in 
in its own plane, and without confusion from the other. We do 
not refer to these hexagons as an instance of the interior mem- 
brane referred to in the passage just now extracted, which seems 
P 
every specimen, and fragment, whether lying flat or edgewise. 
he striz are similar, only more difficult to distinguish with ae- 
curacy, to the fine diagonal markings on the surfaces of ‘Trice- 
ratium, Actinocyclus, Coscinodiscus, and other genera which have 
large hexagonal cells. - 
An able optician from Berlin says that the importance of spher- 
ical correction is but imperfectly understood in Germany: we 
thus find accounted for the mistakes of Ehrenberg, which have 
caused so much surprise, and Dr. Hannover’s omitting all men- 
tion of a screw collar, in a work of such merit as to be selected 
for translation into English. 
Arr. XXII1.—Further Notes on Cereus giganteus of Southeast- 
ern California, with a short account of another allied species 
in Sonora; by Dr. Georce Enceimann, St. Louis, Missouri. 
In question in fower. ‘These materials enable me to furnish the. 
ollowing detailed character. 
Catis angulatisque albidis demum cinereis, radialibus 12-16 imo 
Stmmisque brevioribus, lateralibus (preecipue inferioribus ) longi- 
oribus robustioribus subinde cum aculeis adventitiis paucis seta- 
els summo areola margini adjectis ; aculeis centralibus 6 robustis 
albidis basi nigris apice rubellis demum totis cinereis, 4 inferiori- 
* See this Journal, New Series, vol. xiv, page 335, Nov., 1852. 
