Prof. H. A. Nicholson — New Palceozoic Polyzoa. 33 



striae and annulations of growth. Owing to the obliquity of the 

 calice, the dorsal surface of the corallum is nearly twice as long 

 as the opposite or ventral surface; and the greatest thickness is 

 attained at a point situated about three inches above the base, or at 

 about one-half of the total length. The only individual observed 

 had the following dimensions : Length measured along the dorsal 

 surface, six inches ; along the ventral surface, three inches and a 

 half. Greatest thickness, at three inches above the base, about three 

 inches and a half. Diameter of calice, four inches and a half; 

 depth of calice about one inch. 



This fine species is most nearly allied to C. vesiculosum, Goldfuss ; 

 but it is distinguished from this and all other recorded species of 

 the genus, by its comparatively gigantic dimensions, its very rapid 

 expansion from the base upwards, and the striking obliquity of the 

 calice. When viewed in profile (as in PL I. Fig. 1), its outline 

 appears to be somewhat rhomboidal. This, however, is not a 

 natural or essential appearance, but is due to the fact that the 

 dorsal surface, in the individual examined, is abruptly geniculated 

 at about the middle of its length. There is, however, no reason for 

 supposing that this feature would prove to be a normal one in the 

 species. 



Locality and Formation. — Hamilton Group, Arkona, Township of 

 Bosanquet, Ontario. 



EXPLANATION OF PLATE I. 

 Fig. 1. — Cystiphyllum siqierbam, Nich., viewed in profile, of the natural size. The 



single dark line shows the outline of the calice as seen in a front view. 

 Fig. 2. — Cystiphyllum Ohioense, Nich., of the natural size. 2a. Calice of the same 



viewed from above, of the natural size. 

 Fig. 3.— Fragment of Cystiphyllum fruticosm?i, T8ich., of the natural size. 3a. Calice 



of one of the corallites of the same, slightly enlarged. 

 Fig. 4. — Cystiphyllum squamosum, Nich., viewed from the front, of the natural size. 



4«. Profile view of the same. 4b. Profile view of another individual of the same, 



in which a secondary calice has been produced at right angles to the primary 



calice. All these specimens are silicified, and are covered with "Beekite- 



markings. " 



IV. — Descriptions of New Species and of a New Genus of 



POLYZOA FROB1 THE PALEOZOIC EoCKS OF NORTH AMERICA. 



By H. Alleyne Nicholson, M.D., D.Sc, F.E.S.E., 

 Professor of Biology in the College of Physical Science, Newcastle-on-Tyne. 



(PLATE II.) 

 Genus Heterodictya, Nicholson. 



Polyzoary (?) forming a simple, flattened, unbranched, two-edged 

 frond, with sub-parallel sides, consisting of two series of cells, the 

 bases of which rest upon opposite sides of a thin longitudinally - 

 striated central membrane or laminar axis, from which they pass 

 obliquely outwards in opposite directions. The cells open in longi- 

 tudinal rows on the two flat or slightly convex surfaces of the frond, 

 and have the form of more or less cylindrical tubes, which are septate 

 or are divided transversely by a series of well-developed tabulee. 

 In the only species known the cells of a few of the median rows of 

 decade ii. — VOL. II. — no. i. 3 



