1869.] 381 [Hagen. 



Mr. Ernest Papendiek exhibited a specimen of the Euro- 

 pean Silpha atrata^ one of twenty sj^ecimens taken from the 

 dead body of a toad in Milton, Mass. 



Dr. H. Hagen remarked that Prof Ratzeburg had recently 

 stated, in a letter to him, that he had' carefully studied "Ich- 

 neumonosis," or the prevalence of hymenoj^terous parasitism, 

 in the insects injurious to forest trees, and found that for 

 many years it had carried off ten per cent, of the number of 

 such insects. In 1867 and 1868, years in which the forests 

 had suffered unusually from obnoxious insects, this ratio had 

 been reduced to between one and two per cent., while, at the 

 same time, " Mycetinosis," or the prevalence of fungoid para- 

 sitism, had increased to between forty and fifty per cent. ; a 

 balance of destructive power seemed to be always mamtained 

 between the two forms of parasitism. Mycetinosis had espe- 

 cially checked the ravages of the very destructive caterpillar 

 of Bomhyx pini. 



April 7, 1869. 



Vice President Mr. T. T. Bouve in the chair. Twenty-four 

 members present. 



Mr. William Foster of Brookline and Mr. Heniy Cutter 

 of Boston were elected Resident Members. 



On behalf of the author, the Secretary presented the fol- 

 lowing paper: — 



On New and Imperfectly ELnown Echinoderms and Corals. 

 By a. E. Verrill. 



ECHINOIDEA. 



Agassizia subrotunda Gray. 



Catalogue of recent EchiiiiSa of the British Museum, p. 6.3, pi. iii, 

 fig. 2, 1855. 



Two specimens collected at La Paz, Gulf of California, by Capt. 

 J. Pedersen, agree perfectly with Gray's description and figure of 



