Mineralogy and Geology. 397 
and some other species is noe with a peculiar, convoluted internal 
plate, resembling a shell of a Bulla or Scophander, placed with its 
longer axis so as to colada i that of the body of the crinoid. This 
is illustrated by a wood-cut on p. 191. 
The genus Steganocrinus has also the structure of Actinocrinus in th 
lower part, but with: “Rays, from the third primary radial pieces, form- 
ing dead sailiisids free arm-like appendages, either bifurcating or sim- 
ple, are covered their entire length above gf oa Pei and 
eevee on each side with a row of alternating true a Vault wit 
a subcentral proboscis.” These arm-like peas eks are s gabhlas, with om 
satibabangal ie arranged along the sides,—opening out into the 
grooves of the tr 
On page 220 hers are some figures illustrating the wonderful strue- 
ture of the vault of Gilbertsocrinus. It is there shown that this s genus 
is Dae with Z'rematocrinus (Frail), ae (Lyon and 
een mistaken lately for arms,* but M. an . have shown that the 
true arms are situated i - the re-entering angles between them. There 
numerous important improvements in the oo of ee 
here, We may be amet fenting . remark on the affinities the 
Xi cette and the Hurypterida that the beautiful specimens of £ 
: any 
it were, in the buckler of Limulus the ‘bien segments of Hu ne us. 
* John Rofe, Esq., F.G.S., has figured (Geological Magazine, wok ie ph se 
English tat, portions of these dpecdages which he maintains to ~ ad 
remains of the arms. They are evide ently, however, merely projecting 10 ot 
Am. Jour. Sc1.—Seconp SERIES, voE XLIII, No. 129,—Mar, 1867. 
5) 
ie 
