185 



have in all cases found the markings to be coincident unequivocally 

 with the cut of the wing. It will be seen, however, that in all the 

 species it does not hold, as in P. protodice, that the female is the 

 darkest. 



Two of the species I have described from Western America, P. 

 venosa and P. pallida^ represent respectively the P. napi and P. rapce 

 of Europe. It will be noticed in the European species that each has 

 the same plan of ornamentation upon the upper surface of primaries, 

 namely, a large apical and small submarginal central spot, and that 

 the peculiar distinction between the two is found in the presence or 

 absence of the dark scales bordering the nervures of the secondaries. 

 Just so is it in the Western American species, separated most charac- 

 teristically from one another by the same distinction in the under 

 surface of the secondaries, and linked together in the same way by 

 certain characters of ornamentation (which, however, are not bor- 

 rowed from its Eiiropean congeners), that is, by the presence in the 

 males of the bent band of the inner margin of primaries, and a small 

 submarginal central spot. But when we turn to Eastern America 

 we find this striking circumstance, that P. oleracea, within its own 

 wide range of variation represents both P. rapes and napi of 

 Europe, and both P. pallida and venosa of the Pacific coast ; — and 

 what do we discover here, but that, discarding the strict lines of de- 

 marcation which separate alike P. rapce and napi and P. pallida and 

 venom, it follows instead, with remarkable similarity, the range of 

 variation discovei'able in P. protodice^ as before described, a species 

 much farther removed from it in the genus than are they, thus simu- 

 lating rather its geographical neighbor than its nearest congeners. 



P.frigida and P. marginalis appear to have no true representatives. 



Prof, Agassiz presented a catalogue of the Koninck library 

 recently added to the Zoological Museum at Cambridge, 

 which would be accessible to all students of Natural History, 

 as soon as it could be put in order. The collection consists 

 of 3,000 works, chiefly paleontological, making between 

 5,000 and 6,000 volumes. 



Prof James Hall, of Albany, corresponding member, ex- 

 hibited some very interesting fossils, chiefly crinoids, from 

 the carboniferous and lower Silunau deposits of the West. 



He exhibited also a table, drawn np on the plan of Bar- 

 rande's, illustrating the vertical distribution of Trilobites and 

 allied fossil forms in the Quebec group of Paleozoic rocks, 

 based on Sir William Logan's investigations, and showing 

 that certain genera pass from tlie primordial to the lower 

 Silurian, which are, therefore, beds of passage. A discussion 



