220 Reviews — Wyville TJiomson's ''Depths of the Sea." 



particularly the imbricated arrangement of the plates over portions 

 indicating a circle at least four inches in diameter, caused great 

 difficulty in referring it to its place. Edward Forbes examined it, 

 but would not hazard an opinian. The general impression was that 

 it must be the scaly peristome of some large urchin, possibly of a 

 large Cyphosoma, a genus abundant in the same bed. Some years 

 after the discovery of the first specimen, a second was obtained by 

 the Eev. Norman Glass, from Charlton, in Kent, This specimen 

 appeared at first to solve the difficulty, for it contained in the centre 

 a well-developed ' lantern of Aristotle ' ; there then was the peris- 

 tome of the urchin of which Mr. Mower's specimen was the 

 periproct. The late Dr. S. P. Woodward examined the two 

 specimens carefully, and found that the question was not so easily 

 settled. He detected the curious reversal of the imbrication of the 

 plates in the ambulacral and inter-ambulacral area described in 

 Caheria, and at one point he traced the plates over the edge of the 

 specimen, and found that they were repeated inverted on the other 

 side. With great patience and great sagacity he worked the thing 

 out, and came to the conclusion that he was dealing with the 

 representative of a lost family of regular echinids. 



" Woodward names his new genus EeMnoihuria, and describes the 

 Chalk species, E. floris, almost as fully and accurately as we could 

 describe it now, with a full knowledge of its relations — for Echino- 

 ihuria is closely related ,to Caheria and PTiormosoma. In all 

 essential family characters they agree. The plates imbricated in the 

 same directions and on the same plan, and the structure of the 

 ambulacral area, which is so special and characteristic, is the same. 

 EcJiinothuria differs from Caheria in the wider inter-ambulacral and 

 ambulacral plates, in the smaller amount of overlapping, and in the 

 absence of membranous intervals -^ and from PTiormosoma it differs 

 in having the structure and ornament of the apical and oral surfaces 

 of the tests the same. 



" As the genus Echinothuria was the first described, I have felt 

 justified in naming the family the EcMnothuridce. I have done this 

 with the greater pleasure, as it brings into prominence a term 

 suggested by my late friend Dr. Woodward, whose early death was 

 a serious loss to science." (p. 164.) 



Speaking of the Lily-Encrinites, Prof. Wyville Thomson says : — 

 Both on account of their beauty and extreme rarity, and of the 

 important part they have borne in the fauna of some of the past 

 periods of the earth's history, the first order of the Echinoderms, 

 Crinoidea, has always had a special interest to naturalists ; and, on 

 the watch as we were for missing links which might connect the 

 present with the past, we eagerly welcomed any indication of their 

 presence. Crinoids were very abundant in the seas of the Silurian 

 period ; deep beds of Carboniferous Limestone are often formed by 

 the accumulation of little else than their skeletons, the stem joints 

 and cups cemented together by limy sediment ; and dozens of the 

 perfect crowns of the elegant Lily-Encrinite are often scattered over 

 the surface of slabs of the Muschelkalk. But during the lapse of ages, 



