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THE PALEONTOLOGY OF MINNESOTA. 
[Anomalospongla. 
plates of the Receptaculitide than does the knob-like sixth ray sometimes seen in 
Hyalostelia smithit Young and Young, sp., and but little better than in the numerous 
sponges in which the summit ray is wanting entirely. On the whole it compares 
best with the condition commonly presented by the surface spicules of lithistid 
sponges. (See fig. 1b and c¢.) 
The next point to be compared is the horizontal rays. A fundamental difference 
is at once evident in this, that in the Receptaculitide there are four of them arranged 
at right angles so as to form quadrangular interspaces ; while in Anomalospongia 
there are only three, with the interspaces triangular. In the Receptaculitidw, too, 
the horizontal rays overlap not at all or only sparingly, and when they do the over- 
lapping extremities lie side by side and parallel with each other, and not, as in 
Anomalospongia, over each other. In the latter the crossing and interweaving of the 
rays is a marked feature, and not even approximated by the conditions prevailing 
in the Receptaculitidw. As regards their duplex character in Anomalospongia it suf- 
fices to say that nothing of the kind is known in any of the Receptaculitidw. 
The vertical or entering ray of Anomalospongia is on the whole very similar to 
that ray in Receptaculites, but even more like that in Ischadites, and, if true relation- 
ship exists between them, it is here that we find it expressed with much greater 
obviousness than in any other feature held in common by them. Still, even here 
some important differences are apparent. In Ischadites, which as said presents the 
greatest resemblance to Anomalospongia, and therefore alone need be compared, the 
vertical rays are entirely separate from each other, and project freely into the 
central cavity, the continuity of the wall being formed in part by contact between 
the horizontal rays, but mainly by the overlapping summit plates. In A. reticulata, 
on the contrary, each vertical ray is in contact, normally, with six of its neighbors, 
so that the task of maintaining the shape of the sponge, was performed chiefly by 
this part of the spicules. 
Other points of difference are noticed in the uniform size and in the arrangement 
of the spicular elements of Anomalospongia when compared with the true Receptacu- 
litide.* In the latter they are small at the nucleus and increase gradually in size to 
the periphery ; with the arrangement in regular curved intersecting lines closely simu- 
lating a common style of engraving on watch cases. In Anomalospongia, however, 
the pieces are of nearly the same size on all parts, and the arrangement that merely 
which would result from placing equal hexagonal pieces in contact with each other 
on all sides. 
A feature in which Anomalospongia agrees with Receptaculites, but not more so 
than with other very different sponges (Geodia clavata Hinde), is the peculiar neck-like 
*Not applicable to Spwrospongia, Pengelly, which it seems to me has little claim to association in the same family with 
Receptaculites, © 
