1883.] . natural sciences of philadelphia. 95 



April 24. 

 The President, Dr. Leidy, in the chair. 

 Thirty-nine members present. 



The following papers were presented for publication : 

 " On the Structure of the Skull of the Hadrosauridse," b}' 

 Edward D. Cope. 



"On some Vertebrate Forms from the Permian of Illinois," by 

 Edward D. Cope. 



A Social Heliozoan. — Prof. Leidy exhibited drawings and made 

 some remarks on a singular Heliozoan recently observed by him. 

 His attention had been directed to it by Mr. Edward Potts, who 

 discovered it, contained in considerable numbers in water, with 

 vegetal debris, from Lake Hopatcong, N. J., where it had been 

 obtained last autumn. The animal occurred mostly in groups 

 composed of numerous individuals. One of these groups, of 

 irregular, cylindroid shape, 0*84 mm. long b}^ 0*36 mm. broad, was 

 estimated to contain upwards of a hundred individuals. They 

 reminded one of a mass of tangled burs. Thej^ remained nearly 

 stationary even for twenty-four hours, and exhibited so little 

 activity, that without careful scrutiny they might readily' be taken 

 for some inanimate structure. The individuals composing the 

 groups appeared to be connected together only by mutual attach- 

 ment of their innumerable rays, and none were observed to be 

 associated b}' cords of protoplasm extending between the bodies 

 of the animals, as seen in Raphidiophrys elegans. The individuals 

 associated together were of two kinds : those which were active, 

 and a smaller proportion which were in an encysted, quiescent 

 condition. 



The active individuals resembled the common sun-animalcule. 

 The body was usually spherical or oval, but variable from con- 

 traction, colorless, granular and vesicular, with a large central 

 nucleus more or less obscurely visible and variably granular, with 

 three or four or more peripheral contractile vesicles. The body 

 had a_ thick envelope of delicate protoplasm, with innumerable 

 and immeasurably fine, straight spicules. The envelope with the 

 spicules extended in numerous conical rays, from which pro- 

 ceeded numerous immeasurably fine granular rays. The encysted 

 individuals presented the same essential constitution, except that 

 the body was regularly spherical, enclosed by a structureless 

 envelope or membrane, contained no contractile vesicles, and the 

 enveloping protoplasm was devoid of granular rays. The body 

 of the active individuals measured from 0*024 to 0*036 mm. in 

 diameter; in the encysted individuals, usually about 0*02 mm. 

 An active individual, with the body 0*033 mm. in diameter, with 

 its envelope was 0*0,55 mm. in diameter. An encysted individual, 

 with the body 0*02, with its envelope was 0*036 mm. 



The active individuals were observed to feed on two species of 



