FOSSILS— THEIR A'ATURE AND INTERPRE7\4TI0X. lOI 



ScrtularicLne) are also abundant in a few zones in the Paleo- 

 zoic rocks. Figures 12, 13, 14. 



4^4 * 



Fig. 13. Fig. 14. 



Fig. 13. — Graptolite. Diplograptus pnlmeus Vtaxr. Silurian. (S. and D.') 



Fig. 14. — Coral. Parasniilia centralis Mant. sp. Cretaceous A^ corallite, longitudinally 

 sectioned ; By the same seen from above ; s and 1-5 = septa, c — columella. 



Echinodermata were represented in fossil form, developing 

 some hard parts in each order, viz. : Crinoidea, Blastoidea, 

 Cystidea, Ophiuroidea, Asteroidea, Echinoidea, and even the 

 Holothurioidea probably recognized in the spiculje. The 

 Solecida (parasitic worms, whether grouped with the Echino- 

 dermata, or with annelids under Vermes) are all soft, and do 

 not come within the province of the paleontologist. Figures 

 15-19. 



Vermes. — Among the Vermes (the leeches, earthworms, 

 and sea-worms) there are some which produce earthy cases 

 of mud, others have left their tracks where they bored 

 through the tenacious mud ; also teeth have been found, sup- 

 posed to belong to thfe group. (See Serpula, Spirorbis, etc.) 

 Still, these are rare fossils, and probably represent but very 

 imperfectly the worms living in ancient seas. Figure 20. 



Arthropoda, — Of the Arthropoda, including all those ani- 

 mals composed of definite segments arranged longitudinally, 

 one behind the other, and the locomotor appendages of which 

 are jointed or articulated to the body, we have four great 

 classes: Crustacea, Arachnida, Myriapoda, Insecta. All of 

 these produce a more or less enduring, horny or calcareous crust 

 or case, within which the soft parts are contained, making the 



