THE CRETACEOUS PERIOD. 267 
daris, may be mentioned as being all important Cretaceous 
groups. 
Coming to the Annulose Animals of the Cretaceous period, 
Fig. 191.—Galerites albogalerus, viewed from below, from the side, and from above. 
White Chalk. 
there is little special to remark. The Crustaceans belong for 
the most part to the highly-organised groups of the Lobsters 
Fig. 192.—Dzéscoidea cylindrica ; under, side, and upper aspect. 
Upper Greensand, 
and the Crabs (the Macrurous and Brachyurous Decapods) ; 
but there are also numerous little Ostracodes, especially in the 
fresh-water strata of the Wealden. It should further be noted 
that there occurs here a great development of the singular 
Crustaceous family of the Barnacles (Zepadide), whilst the allied 
family of the equally singular Acorn-shells (4a/anide) is feebly 
represented as well. 
Passing on to the Mollusca, the class of the Sea-mats and 
Sea-mosses (/o/yzoa) is immensely developed in the Cretaceous 
period, nearly two hundred species being known to occur in 
the Chalk. Most of the Cretaceous forms belong to the family 
of the Lscharide, the genera Eschara and Escharina (fig. 193) 
being particularly well represented. Most of the Cretaceous: 
Polyzoans are of small size, but some attain considerable di- 
mensions, and many simulate Corals in their general form and 
appearance. 
