SOME INVERTEBRATE EXOSKELETONS 



SPICULES OF CALCIUM 

 CARBONATE 



FIG 67 SIMPLE SPONGE AND SCHEMATIC CROSS SECTION {PORIFER) 



PLATES OF CALCIUM 

 CARBONATE 



FIG. 68. TEST OF A SEA URCHIN (ECHINODERM) 



SHELL OF CALCIUM 

 CARBONATE 



LINE OF MANTLE 

 ATTACHMENT 



PLATE OF 

 CHITIN 



FIG. 69 SHELL OF A CLAM {MOLLUSC) 



FIG. 90. SECTION OF ABDOMINAL 

 SEGMENT OF LOBSTER (ARTHROPOD) 



Figs. 87, 88, 89, and 90. — Some types of invertebrate exoskeletal and supporting 

 structures. (Fig. 87 partly after Kiihn: Grundriss der allgemeinen Zoologie. Georg 

 Theime, Leipzig.) 



