Mineralogy and Geology. 119 
Lower Silurian, 86 from the Upper Silurian, 115 from the Devonian, 
and 452 from the Carboniferous rocks. 
d to synonymy, i oup like this, snicladiog so many close 
allied species of which only dancriptions have been published, there will 
of course, be differences of opinion; and beyond the instances where 
direet Fee cance of authentic examples of the allied forms have been 
ases where no figures have been published), any views on the 
within can only be regarded as mere opinions, that may be right or ma 
e wrong. Some of the supposed synonyms are believed by the writer 
of this notice to be distinct abet while he has no doubts whatever in 
regard to the distinctness of other forms, between which comparisons 
are suggested. These sel et selotisirene will be useful even when the 
species alluded to are distinct, as hints to those who may have the means 
to make comparisons, and wi ish to do so, with the view of studying the 
at pl 
accuracy and completeness of this valuable Sees there are a pare 
names not accompanied by correct diagnoses, great confusion would re- 
sult, since many of the destespasonn published ey oe Miller, Link, 
and various other early investigators, as well as by many later ones, 
would apply equally well to almost any other genus of the alle family ; 
while not unfrequently the few characters given by them were not all 
strictly applicable to the particular type named. Where they cited 
i t t 
regard to the particular genera they had in view, their names have been 
adopted notwithstanding the defects of their diagnoses. Where an 
author has given us the means of peng beyond a reasonable doubt, 
Bell lerophon Montfort, yee no one hase because 
its author described it as a chambered hell —siplyf A i “ fact that 
his _ —_ ata pinecn what genus he ha 
gain, cannot agree with the author of a: cestalogns in citing 
Gilbertsocrinue ree as a aynee ym of Rhodocrinus Miller, (although 
st wot may se . specimen of Goniasteroidocrinus or 
with i and pseudo-brachial appendages unbroken. Inns Mr 
Billings hinted at the probability that Gilbertsocrinus would be found to 
* See note on this subject in Proc. Phil. Acad. Nat. Sci, Aug., 1865, p. 168, 
a 
