cohstitutioh or chalk and fliht. 
149 
Organic Remains found in the Chalk. Vertebrata .—More than 
3000 species of aquatic animals have been recognised by palaeonto¬ 
logists in the Chalk. Although no relics of either Mammals or 
Birds have been discovered in the English Chalk, yet high-class 
Reptiles are well represented by scattered remains of Pterodactylus, 
Mosasaurus , Leiodon, Raphiosaurus, Coniasaurus, Dolichosdurus , 
Chelone , Polyptychodon, Plesiosaurus, and Ichthyosaurus * Of Fishes 
there are innumerable specimens of teeth, scales, and hones, represent¬ 
ing three genera of Chimseroids, about fifteen genera of Plagiostomes 
(Sharks and Cestracionts), twelve genera at present grouped as 
Ganoids, and twenty-two genera of Teleostean Fishes, f Rone of 
these, however, have supplied any considerable quantity of material 
in the formation of the Chalk. 
Invertebrata. Molluscs, Annulosa, Echinoderms. —The Cephalo- 
podous Molluscs are in some beds numerous; as Belemnites 
(. Belemnitella ), Nautilus , Ammonites , Scaphites, Turrilites, and 
Baculites. Excepting Nautilus, they have no living representatives. 
Their remains have added no appreciable mass to the Chalk. The 
Gastropoda are relatively rare in the Chalk, but are not wanting in 
numbers at places. The Conchifera , especially the Monomyaria, or 
those related to the oyster, spondylus, pecten, scallop, and perna, 
are abundant, and whole beds are composed of the Inoceramus shell 
and of its constituent prisms in a loose disintegrated condition. The 
Bimyaria are not absent, though rarer. Of the Brachiopoda {Mollus- 
coida ), Kingena , Magas, Argiope, Crania, Terebratulina, Terebratella , 
Terelratula , Waldheimia, and Rhynchonella , are well known for 
their occasionally local abundance. Of the Annulosa, none of the 
Cirripedes and Crustaceans (some as high as the Lobster group) 
are abundant, except the minute bivalved Ostracoda {Cy there, etc.), 
and these occur in crowds among the washings of different beds of 
Chalk. Of Annelids, there are numerous examples of the tube- 
shelled Serpulee. 
The Echinodermata are abundant and varied. The Crinoids 
are Marsupites, well known in certain bands of White Chalk at 
Margate and near Arundel; and Bourgueticrinus and Pentacrinus , 
both of which help to make up some beds by their innumerable 
ossicles. Of the Echinoids, many species of Cidaris, Biadema, 
Cyphosoma, Echinopsis, Salenia, Echinoconus or Galerites, Biscoidea , 
Echinocorys or Ananchytes , Holaster, Epiaster, and Micraster, are 
well known. The flint casts of some are so abundant in the Chalk 
districts that the country-people know them as fairy loaves 
(. Ananchytes ), fairy helmets ( Galerites ), shepherds’ crowns 
{Cidaris), and fairy hearts ( Micraster ). These sea-urchins and 
sea-eggs have evidently added much to the sea-bed of their day. 
Their tests or shells are often found whole in the Chalk, with 
their plates and spines quite perfect; very often indeed the tests 
are destitute of spines, and were dead before being buried, and 
* See Dixon’s ‘ Geol. Sussex,’ 2nd ed., p. 407, etc. 
t Ibid., pp. 387-406. 
