ORGANIC DEPENDENCE AND DISEASE 



73 



Fig. 60. Two speeimeus of the Devonian erinoid, Taxocrinus lohatti-s Hall, with a 

 coiled snail (Platyostoma) attached to the dome. Canandaigua Lake, N. Y. 

 (h. by courtesy of Mi-. Frank Springer.) 



A singular and single instance of similar concurrence has 

 been found in the Portage Upper Devonian (West Hill 

 shales) of Naples, N. Y., a baby Melocrinus, not above one- 

 half inch in length (calyx) to which is attached a baby 

 Platyceras of about the same size. This is a convincing 

 evidence of the early age at which this adaptation became 

 effective, though it is no proof that the conjunction may not 

 have been broken in later life. It 

 is certainly extraordinary that this 

 parasitized young condition is the 

 only one recorded in these rocks, 

 while Melocrinus is the only abun- 

 dant erinoid in the Lower Portage 

 fauna. 



The Devonian faunas, in these 

 cited instances, have thus furnished 

 us with instances of the growing- 

 habit of this parasitic attachment. 

 We find it to be occasional and spo- 

 radic, desperate and often ill-ad- 

 justed arrangements which seem to 



T 1 1 J T i j_ Ji T J Fig. 61. Young Melocrinus 



have brought disaster to the hosts. ^ti young snail attached. 



We see cases, as Melocrinus mic- Upper Devonian. 



