572 MANUAL OF NATURAL HISTORY. 



Echinite, in the upper strata. There are also found 

 numerous species of Turban-Urchins (Cidaridw), as 

 the elegant Hemicidaris, and others. Species of 

 Glypeus, or Buckler-Echinite, Gyphosoma, and Sa- 

 lenia, are also present. Among the Grinoidea, 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 a 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, 

 Astrem, Fungice, Meandrince, and Garyophyllice 

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

 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 Xantkidium, 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 

 poly gastric 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- 



