SECTION IV., 1901 [109 ] Trans. RS. C. 
IX.—Hyolithes gracilis and related forms from the Lower Cambrian of 
the St. John Group. 
By G. F. MATTHEW, LL.D. 
(Read May 23, 1901.) 
From the strata of Division 1, Band d, in the Cambrian Basin of 
St. Martin’s, the author in 1885 described the species [yolithes (Cam- 
erotheca) gracilis.’ (See figs. 1, 14 and e.) 
l'en years later he described another form, H. gracilior, from Band b 
of the same division, and in the same basin ; similar in form, but 
smaller and more slender.? (See figs. 2a and 0.) 
Subsequently he found another form of nearly similar proportions, 
but still more slender, and with a shorter dorsal lip, which he would 
distinguish as :— 
mut. GRACILLIMUS n. mut. Figs. 3a-d. 
This form is from the P. Eteminicus, Band c?, or the P. lamellatus 
Band c1, as there is a record of the finding of these species of 
Paradoxides in the beds from which this Hyolithes came. It is from 
the St. John Basin, and its stratigraphical position would be between 
the other two. The tube, for a Hyolithes, is of very slender proportions, 
and if it were not for the form of the orifice it might be referred to 
Orthotheca. Indeed, Dr. Holm has referred several slender species, 
with a low-arched lip, to Orthotheca. 
The tube is much flattened on the dorsal side and for this reason 
as well as for the arched lip, should be placed under Hyolithes. 
The lateral angles are rounded, and the convex ventral face is slightly 
ridged or keeled along the middle. The upper two-thirds of the tube 
is smooth and the substance of the shell thin. The lower third is 
thicker and has about four chambers in the proximal end. 
Detached examples of what appear to be the larval tube, are found 
on the same layers as this shell. These are flattened in the shale, while 
the adult tube is filled with spar or clay and retains its original form. 
The supposed larval tube runs to a slender point. 
The apical angle varies in different parts of the tube ; thus the 
proportion of width to length in the supposed larval tube is 1 to 13 ; 
in the lower part of the calcified adult tube it is 1 to 8-6 and in the 


1 Trans. Roy. Soc. Can., vol. III., sec. IV., p. 50, pl. vi., figs. 2,.2@ and 26. 
2 Trans. N. York Acad. Sci., XIV., p. 130, pl. vi., figs. 3a and 3b. 
