66 EVOLUTION IN THE PAST 



minute foraminifera were smaller than many of their ances- 

 tors in Carboniferous seas. Sponges were very poorly 

 represented. In coral-life reef-building was almost brought 

 to a standstill. Starfishes and brittle-stars seem to have 

 been quite under a cloud. Cystids, long languishing, died out 

 early in the Period. Great havoc had been wrought in sea- 

 lily ranks. All the sanitary reformers apparently had been 

 wiped out : and crinoidal fortunes seem to have been in the 

 keeping of an old family that had struggled on from Ordo- 

 vician times (Cyathocrinidce). But it was not all a catalogue 

 SEA-URCHINS of woe. Sea-urchins of Devonian type, both flexible and 

 inflexible, had indeed been nearly exterminated ; but " rude 

 forefathers " of some modern urchin-families were just 

 beginning to appear. These were enclosed in rigid tests, 

 with vertical plate-rows reduced to the number that now 



POLYZOANS obtains (Hemicidaris, Cidaris). Polyzoan colonies were in 

 great force. Those of the open-mouthed type had recovered 

 their ascendency ; but the rival group was well in evidence 

 LAMPSHELLS (Fenestella). Brachiopods or lampshells, though reduced in 

 variety, made a good display, especially in Asiatic waters. 

 Species with anchor-spines continued most prominent ; but 

 no giants were now in their ranks (Productida). Other forms 

 in " butterfly " shells also much in evidence in Carbonifer- 

 ous seas were abundant (Spirifer) ; and several other 

 lampshells of remote lineage were still clinging to the rocks. 

 BIVALVED There is no great progress to report among bivalved 

 MOLLUSCS molluscs ; but they attested their character as a rising group 

 by new forms of ark-shells (Schizodus) ; and by the evolution 

 also of some small forms (Bakewellia), founders of a present- 



UNIVALVED day family of pearl-oysters (Pernidai). Univalves exhibited 



MOLLUSCS little or no progress. The most prominent at this time were 



creatures in bell-shaped shells of Silurian pattern (Bel- 



NAUTILOIDS lerophori). Apparently all species of nautiloids in slightly 

 curved shells had died out ; and those in straight shells were 

 represented by only one genus that had persisted from the 

 Cambrian (Orthoceras). Several genera, however, in shells 

 more or less resembling the coiled shells of the living nautilus, 

 were about the seas (Stenopoceras, Pselioceras) and the 

 long competition between the " uncoiled " and the " coiled " 



