102 Xatural Ilistoo'y Society of JB., Bulletin No-. IV. 
were making their Avay into the St. Jolm Basin was a period of 
decreasing volcanic action and of gradual subsidence in that area. 
In concluding this article I quote a letter of Prof. Alpheus Hyatt 
of Boston, well known for his researches among the Cephalopods and 
Sponges, which relates to one of the new forms noticed in the pre- 
ceding paper. Prof. Hyatt had very kindly offered to advise me in 
reference to difficult points connected with the fossils of the St. John 
Group, and I therefore availed myself of this opportunity to place 
before him the various specimens of pteropodous shells bearing upon 
the possible early connection of the pteropods with the cephalopods. 
Unfortunately the letter giving the details of his examination of 
these fossils has been lost in transmission, but the general results of 
the investigation are given in the summary quoted below from a later 
letter. By way of preface to Prof. Hyatt’s letter I may say that 
more than one of the early pteropods of the St. John Group are 
remarkable for the presence of several distinct septa at the base of 
the tube. There are two such species in the band b ; another, but a 
longer and narrower kind, is found in the band c, and this or a similar 
camerated shell occurs in the band d. Of these species (referring, 
however, chiefly to the oldest) Prof. Hyatt says (3rd February, 
1885) : 
“ I kept no notes of the details I had observed ; my results, how- 
ever, were quite definite in respect to the main points. These were : 
(1). The fossil is a Hyolithes allied to II. undulatus^ Barr. Syst. 
Silur. pi. 11, f. 29. (2). The aspect of a siphon is due to the com- 
})ression of the sharper against the flatter side and the form of the 
sutures, which favors this impression. Barrand figures, as I found 
after arriving at this decision, a similar case, pi. 15, figs. 35, 35a, 
of a closely allied species, II. elegans. (3). The sutures are similar 
to those of II. elegans in curvature, but wider apart. These fossils 
with their distinct septa are startlingly similar to certain forms of 
Nautiloidea, but there is no siphon. They, however, confirm Von 
Jhernig’s and my opinion that the Orthoceratites and Pteropods 
have had a common, but as yet undiscovered, ancestor in ancient 
times.” 
