REPORT OF THE DIRECTOR I9II 45 



oyster is now pretty well understood. Embracing the oyster with 

 its flexible arms and placing its mouth against the edges of the valves 

 it attaches itself by its suckerlike tube feet to one valve and the 

 other, slowly but persistently and patiently pulling in opposite direc- 

 tion and against the strong pull of the bivalve's adductor muscles 

 which hold the valves together. The slow long pull of the starfish 

 tires out the stronger but less enduring oyster, the valves gradually 

 yield and the incolant falls an easy victim to the eversible gorge of 

 the starfish. A plantation'of oysters is an invitation to the starfish 

 to assemble on the ground, but their omnivorous appetite does not 

 restrict them to this viand alone. Nothing edible is foreign to them. 

 So in the ancient days of the Devonic, the clams and oysters, repre- 

 sented by the abundant Grammysias and Pterineas in these rocks, 

 seem to have drawn the stars to this place, and then they were caught. 

 Nearly every Grammysia or Pterinea found in this layer has a star in 

 or on it, sometimes several about its edges in attitudes suggestive 

 of attack and it is altogether reasonable to believe that the hostility 

 between the starfish and the bivalves had fully developed at this 

 early day in the history of the earth. 



The structure, internal and external, of the Palaeaster is ad- 

 mirably preserved in these examples and among the specimens are 

 a few which show the existence of only four, instead of the normal 

 five arms. 



Fauna of the Snake Hill beds. The organic contents of this 

 formation have been worked out by Doctor Ruedemann and on the 

 basis of their nature he allocates the formation to the lower Trenton 

 The fauna is found in excellent development in shales, grits and 

 cherts along Saratoga lake, and its composition indicates its affilia- 

 tion with the eastern or Atlantic fauna of this time, rather than with 

 the fauna of the interior basin of the continent. 



The nature of this faunal assemblage is indicated by this list of 

 species : 



Dicranograptus nicholsoni Hopkinson 



Diplograptus amplexicaulis Hall 



D. amplexicaulis var. pertenuis Ruedemann 



D. (Mesogr.) putillus Hall 



Climacograptus scharenbergi Lapworth 



C. spiniferous Ruedemann 



Cryptograptus tricornis Carr. mut. insectiformis Ruedemann 



Lasiograptus eucharis (Hall) 



Glossograptus quadrimucronatus Hall mut. pertenuis Ruedemanri 



Corynoides calicularis Nicholson 



Dawsonia campanulata Nicholson 



