NIAGARAN CEPHALOPODS 
297 
Measurements: (Greatest diameter (aver.) 40 mm., least 
(aver.) 38.1 mm.; length, of segments (aver.) 21 mm.; obliquity, 
95 °. 
Occurrence and Locality : The type specimen is in the Univer- 
sity collection and is labelled Niagaran, Delaware county, Iowa. 
Huronia hopkintonensis sp. nov. 
Plate XXXIII, figure 3. 
Siphuncle large, straight, tapers very gradually. The type 
specimen consists of four partly broken segments and a frag- 
ment of a fifth segment. Transverse section apparently circular. 
The segments are strikingly short and broad and are about 
two-fifths as long as wide; their sides slope gradually and the 
upper one-third of each is moderately swollen; the top of each 
turns abruptly inward then obliquely downward beneath the seg- 
ment above. The obliquity of the segmental contact is small. 
A fragment of the septum between the two lower segments is 
double; this is an actinoceran character not present, as far as 
observed, in any other specimen of Huronia at hand. 
The endosiphuncle is central and is two millimeters in dia- 
meter. The actiniform lamellae are very numerous and more 
crowded than in any of the other species here described. 
This species differs from H. vertehralis in its larger size, in 
the proportions of the segments, and in the much less swollen 
anterior ring. 
Measurements: Greatest diameter, (aver.) 55 mm., least 
(aver.) 46 mm. ; length of segments (aver.) 20.6; obliquity, 93°. 
Occurrence and Locality : The type specimen is in the Univer- 
sity collection and is labelled Niagaran, Hopkinton, Iowa. 
Huronia turbinata Stokes. 
Plate XXXIII, figure 4. 
1824. Huronia turtinata Stokes. Trans. Geol. Soc. London, second 
series, Vol. i, pt. ii, p. 203, PI. xxviii, fig. 3. 
Siphuncle straight, round, and tapering gradually. Our 
specimen consists of four segments, the upper and lower imper- 
fect, the two middle ones nearly whole. 
The segments are notably turbinate in shape ; the swollen part 
of each is prominent and a circle passing along its greatest 
periphery is quite well back from the anterior end. The upper 
half of each segment is convex while the lower half is slightly 
concave and smoother than the upper. The maximum and mini- 
