S. P. Sharples on some Crystals of Zinc. 223 
Mr. Emerton as near allies. The oculiferous tubercle and the 
cephalothoracic pit appear to sustain this opinion and if the 
examination of additional material should show that the palpi 
are not forcipulate, but are small and absent from this specimen, 
we should have in the Arthrolycoside, an interesting example 
of what might properly be called an embryonic type. 
The thanks of the author are due to Prof. O. ©. Marsh, and 
through him to Mr. S. H. Seudder and Mr. J. H. Emerton, for 
the kindly interest that these gentlemen have manifested, and 
for their valuable suggestions upon the literature of the subject 
and the affinities of the insect. 
Yale College, New Haven, Feb. 9th, 1874. 
Art. XXVII.—On some Crystals of Zine; by S. P. 
SHARPLES, 8.B. 
(Read before the American Academy, Jan. 13, 1874.) 
This moss was found under the microscope to consist of flat 
ribbon-like crystals, which were deeply striated in the direction 
of their length. Analysis gave ninety- se per cent of metal- 
lie zine, They are very tough and will beara considerable 
amount of bending, while the alloy itself is as brittle as glass. 
Prof. Cooke, in some experiments with zine and arsenic, 
Made some years ago, obtained similar erystals by subliming 
zine in a closed tube, and I have observed these crystals in the 
Prolonges of the zine works in South Bethlehem, Penn. But 
