572 MANUAL OF NATURAL HISTORY. 



Echinite, in the upper strata. There are also found 

 numerous species of Turban-Urchins (Cidaridce), as 

 the elegant Hemicidaris, and others. Species of 

 Clypeus, or Buckler-Echinite, Cyphosoma, and Sa- 

 lenia, are also present. Among the Crinoidea, we 

 find the purse-like Marsupites, and the Pear-Encri- 

 nite (Apiocrinus) from the Bradford clay of Wilt- 

 shire; also the Pentacrinus. A few Asteriidce and 

 Ophiuridce, and a Goniaster, or Cushion-star, are 

 frequent in the white chalk, besides Gonulus and 

 Discoidea of the Cidaridce. Among the Polypi/era, 

 those funnel-shaped bodies, often termed " petrified 

 mushrooms/' occur ; they belong to the genus Ven- 

 triculites, and are very numerous in the Chalk ; Ocel- 

 laria is a beautiful allied genus, and, besides these, 

 Astrece, Fungice, Meandrince, and Caryophyllice 

 prevail. Many Polyzoa also occur, as Eschara, Cri- 

 sia, and Flustra. The shell-like skeletons of Fora- 

 minifera are found in great abundance in the Chalk, 

 thirty genera, comprising two hundred and fifty spe- 

 cies, having been described by M. D'Orbigny. Among 

 these may be observed the crosier-like Lituola, the 

 fan-shaped Flabellina ; the entwined and spiral Tex- 

 tularia ; the globular Xanthidium, and the saucer- 

 shaped Pyxidiculum. The whole mass of the white 

 Chalk, moreover, has been shewn by Ehrenberg 

 almost to consist of the skeletons of Infusoria, or 

 polygastric animalcules, mixed up with well-pre- 

 served Foraminifers. The tabular and nodular 

 masses of Chalk-flints are believed to be composed 

 principally of fossil Sponges, which are often mine- 



