fi. Billings on the structure of the Crinoidea, ete, 51 
;: 
tin as converted into SnO, and the antimony into Sb,O,, cal- 
culated the proportions of the metals from the increase in 
weight. This method, although by no means giving me accu- 
rate results, served very well for rough approximate determina- 
tions. I cite it here simply as an easy and convenient process 
for obtaining a close idea of the constitution of any alloy com- 
posed of the two metals. Possibly the method might’ be so 
modified as to give accurate determinations, 
Art. VII.—Notes on the structure of the Crinoidea, Cystidea, and 
Blastoidea; by E. Bruuines, F.G.S., Paleeontologist of the 
Geological Survey of Canada. 
[Continued from this Journal, IT, vol. xlviii, p. 83.] 
5. On the homologies of the respiratory organs of the Paleozoic 
and recent Echinoderms, and on the “ Convoluted Plate” of the 
mnoidea, 
logues of each other. 
Among the Cystideans we find several genera, such as Cryp- 
14 
_ Weerinites, Malocystites, Trochocystites, and apparently some others, 
Whose test is totally destitute of respiratory pores, being com- 
Big: of simple, sold plates like those of the ordinary Crinoidea. 
1.4 second group of genera, among which may be enumerated 
Caryocystites, Eehinospherites, Paleocystites and Protocystites, 
