1889 .] 
261 
[Foerste. 
Mr. J. E. Humphrey and Mr. Waller R. Davis were elected As- 
sociate Members. 
The following reports were then read : 
THE PALEONTOLOGICAL HORIZON OF THE LIME- 
STONE AT NAHANT, MASS. 
BY AUG. F. FOERSTE. 
I recently found fossils in the limestones near East Point, Na- 
hant, in considerable abundance, of the genus Hyolitlies — the same 
species as those discovered at Locality I, near Hoppin Hill, North 
Attleboro, by Prof. N. S. Shaler, nearly six years ago. In the 
Preliminary Description of Fossils from that region this form was 
referred to Hyolitlies princeps, Billings. The Massachusetts speci- 
mens have the ventral side almost evenly rounded, but the lateral 
angles are of unequal curvature so that the bilateral symmetry 
usually found in this genus is entirely destroyed. The apical angle 
is very low, usually about 6°. The shells as found are often invag- 
inated one within another, a feature which, although probably acci- 
dental, is very likely connected with some structural peculiarity 
which permitted ready invagination in this species, while apparently 
in others it is absent or rare. This fossil has been observed in Massa- 
chusetts in four widely separated localities. The Nahant specimens 
are usually smaller than those described from North Attleboro. In 
the collection presented by Mr. S. W. Ford to Columbia College, 
N. Y., there is a specimen labelled Hyolitlies Emmonsi , Ford from 
Troy, N. Y., which does not accord at all with his description of 
that form but has the inequilateral outline of the Massachusetts 
specimens. Its apical angle is about 8.5°, as well as could be de- 
termined without actual measurement of the same. C. D. Walcott, 
in “ Second Contribution to the Cambrian Faunas,” figures on Plate 
xiy, two sections, / and g, under Hyolitlies communis , Billings, 
which are to a certain extent inequilateral ; it does not accord with 
my own observations on this genus to find the shells ever as much 
thickened as represented by these sections, and I venture as a sug- 
gestion the possibility of invagination in the specimens figured. The 
apical angle of Hyolitlies princeps is so much larger than the Mas- 
sachusetts specimens, viz. : 16°, that I suggest the separation of 
