FAMILY ZYG^SNIDJi. ( 



to take the specific gravity, or to admit of many chemical tests. 

 Before the blowpipe it fused quietly on the edges to a gray 

 enamel, imparting an indistinct reddish-yellow color to^the flame, 

 which changed to green upon moistening the assay with nitric 

 or sulphuric acid. With the sodium test, however, it did not 

 give phosphuretted hydrogen. On platinum wire, with borax, 

 the presence of iron and lime were indicated. It dissolved in 

 nitric and hydrochloric acids with effervescence, with the excep- 

 tion of a slight, black, granular residue, insoluble even on the 

 application of heat. Heated alone in the closed tube there was 

 no trace of water. So far, its blowpipe characters seem to be 

 as anomalous as its general appearance. 



It should be remarked, by the way, that the greenstone to 

 which I have last alluded, forms a dike in what is known as the 

 'coralline formation," while that from the vicinity of "Spouting 

 Horn" is the metamorphic or stratified variety of diorite. The 

 latter contains so much magnetic iron as to have a very decided 

 influence on the needle. Indeed, in the specimens I have 

 examined, the rock seems to owe its dark color and high specific 

 gravity ( very nearly three) fully as much to the magnetite, as 

 to the hornblende, which enters into its composition. 



Cambridge. January, 1864. 



III. Notes on the Family Zygcp.tiidce. BY A. S. PACK- 



( Communicated February 22, 1864.) 



The primary object of the writer in preparing this paper was 

 to give as full an account as possible of the transformations of 

 Ctenucha virginica, and the systematic position of the genus 

 Eudryas. The very close resemblance of the early stages of 

 the former genus to the Arctians both in structure and habits, 

 and the fact that the genus has been recently placed among the 

 Bombycidse by some authors, affords us an opportunity of dis- 

 cussing the characters of the Zygasnidas in contrast with the 

 allied families. For this purpose it has been necessary to study 

 the typical European genera in connection with the American 

 types of the group. For most of my material I am indebted to 

 Messrs. F. G-. Sanborn, Boston, Mass : A. R. Grote, New 



