DR. G. J. HINDE ON RECEPTACULITIDA. 837 
in width in the zonal region, where they are largest, to from -25 to °4 
millim. in the vicinity of the summit-aperture. The character and 
position of the spicules are referred to in the generic description. 
The longest of the vertical spicular rays which I have seen vary 
from 7 to 10 millim. 
This species varies considerably in size and in details of outer 
form ; but in the large collection which Prof. Lindstrom sent me 
from the isle of Gotland there are numerous transitional forms be- 
tween the extremes, so that it is impossible to regard them as more 
than a single species, and in this gradational series there are speci- 
mens closely corresponding, not only to Murchison’s type, but also 
to the forms which by Hichwald, Salter, D. Dale Owen, Meek, Billings, 
and Hall have been described as distinct species. The diversity of 
synonyms given to this single species can be further explained by 
the extraordinary difference of aspect which it presents under dif- 
ferent conditions of preservation. 
Eichwald recognizes the similarity of A. Bronnii to I. Kenigu, but 
places it as a different species because it is not compressed, and the 
surface-markings are absent. The figure of Selenoides iowensis, D. 
Dale Owen, represents the concave basal surface of an individual. 
R. Jonesi, Bill., is a very similar form to Owen’s towensis; the 
figure of its vertical section clearly shows the free termination of 
the vertical rays of the spicules. TZ. antiquus, Salt., which is 
in the Jermyn Street Museum, is simply the impression of a portion 
of the outer surface of an individual which shows no character to 
distinguish it from J. Kaenigu. The MS. name of S. tessellatus, 
Salt., appears to have been given to a specimen which is also in the 
Jermyn Street Museum, and which cannot be distinguished from 
Murchison’s type. ven if this had been a valid species, the spe- 
cific name would require to be changed, since it had been previously 
employed by Winchell and Marcy for an example of this genus. 
The specimens figured under Receptaculites globularis, and R. 2 
by Meek and Worthen, represent the concave bases and the lateral 
areas of two individuals. These authors appear to have followed 
Hall in regarding the base as the summit of the specimen, 
whilst they describe the summit, which, as shown by the figures, 
is obscured by matrix, as a broad base of attachment. The 
R. ohvoensis of Hall and Whitfield is merely an imperfect cast of an 
individual of this species. The base of RA. subturbinatus, Hall, is 
represented as the summit of the specimen. 
Distribution. Lower Llandeilo: Garn Arenig, Wales. Woolhope 
beds Malvern: near Buildwas. Wenlock shales and limestone: 
Dudley, Usk, Malvern, Walsall; Balcletchie and Penkill, Ayrshire. 
Lower and Upper Ludlow: Ledbury and near Ludlow: Pentland 
Hills. Orthoceratite limestone: Reval. Lowest beds of the 
Silurian, at Visby, Westergarn, near Klintehamn, Djupvik, in the 
isle of Gotland. Galena Division of Lower Silurian at Scale’s 
Mound, Illinois, andin Iowa. Niagara group at Waldron, Indiana ; 
Yellow Springs, Ohio. Lower Helderberg Group at Gaspé, province 
Quebec. 
Q.J.G.8. No. 160. 31 
