102 
ORGANIC DEPENDENCE AND DISEASE 
Fig. 94. Palaeosabella prisca (McCoy). Copy of the original figure. 
Fig. 95. The same in the shell of the brachiopod Spirifer from the Chemung 
group (Upper Devonian). 
Fig. 96. Similar clavate tubes in the brachiopod Leptostrophia. Oriskany sand- 
stone (Lower Devonian). 
Fig. 97. Sketch of Palaeosabella tubes converging from the margin toward the 
thickened apex of the brachiopod Spirifer. 
Fig. 98. A similar sketch to show the bend in the tube where the shell is 
thickest. Hamilton group (Middle Devonian). 
Fig. 99. The bivalve Aviculopecten with borings all beginning at a definite 
growth-stage of the shell, outside of which the shell is regular, indicating that 
the mollusk was alive when the borings were started and continued to live 
while they were making. Chemung group (Upper Devonian). 
Fig. 100. The sponge here started in the thickened apical substance of the shell 
of a brachiopod (Leptostrophia) and as it entered the thinner part of the shell 
was forced to take on a flattened form. At the inner end it shows a tendency 
to divide. 
Fig. 101. A hook-shaped boring in the cast of a brachiopod. Oriskany sandstone 
(Lower Devonian). 
Fig. 102. A set of clavate borings in the brachiopod Leptocoelia. Oriskany 
sandstone. 
Fig. 103. A series of these tubes beginning at the margin of the discinoid brachi- 
opod Orbiculoidea. Lower Devonian. Sao Paulo, Brazil. 
