Prof. H. A. Nicholson — New Palceozoic Polyzoa. 37 



Arkona, Township of Bosanquet ; and cutting on the Grand Trunk 

 Railway near Widder, Township of Bosanquet, Ontario. 



Ceramopora Huronensis, Nicholson. Plate II. Figs. 5, 5a. 



Polyzoary forming small patches or crusts, of a rounded or 

 irregular form, from one-quarter to one-third of a line in thickness, 

 growing parasitically upon foreign bodies, and rarely exceeding 

 three or four lines in diameter. Cells radiating from a central or 

 excentric point, about six in the space of one line, partially im- 

 mersed, and elevated towards their mouths, which, when perfect, are 

 of a sub-triangular or crescentic form. 



This species resembles young examples of Ceramopora OMoensis, 

 Nich. ; but is distinguished from adult examples of the same by 

 forming small parasitic crusts, composed of a single layer of cells, 

 which radiate from a generally central point. The cells are also to 

 a greater extent immersed, and are not in such close contact. From 

 C. incrustans, Hall, the present species is separated by its smooth, 

 not nodulose or tuberculated surface. G. Huronensis somewhat 

 resembles the figures of Berenicea (Diastopora?) irregularis, Lonsd. ; 

 but the latter is stated to possess round cell-mouths, and the published 

 description is not sufficiently detailed to allow of a close comparison. 



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

 Bosanquet, Ontario. Growing on the exterior of Cystiphyllum vesi- 

 culosum, Goldfuss, and Heliophyllum Halli, Edw. and H. 



Retepora Trentonensis, Nicholson. Plate II. Figs. 4-45. 



Polyzoary forming a fan-shaped expansion, composed of slightly 

 divergent, sub-parallel branches, which have a width of about one- 

 third of a line. The branches are more or less sinuous in their 

 course, and divide dichotomously at short intervals, usually uniting 

 with adjacent stems so as to form an open network, the fenestrules 

 of which have an approximately oval shape, and are from one to two 

 lines in length. The cells have the appearance of being oblique to 

 the surface, and there are four, five, or six rows of them in a branch. 

 They are also present upon all the areas formed by the anastomosis 

 and conjunction of contiguous branches. The cell-mouths are poorly 

 preserved, but appear to have a long oval shape. The non- 

 celluliferous side is strongly striated with wavy or straight longi- 

 tudinal striae or ridges. 



This species is only known to me by several more or less im- 

 perfect specimens, from which some of the essential characters 

 cannot be determined. It appears to be a genuine Betepora, and to 

 be most nearly allied to B. Rising eri, M'Coy : but the fenestrules 

 of the latter are much smaller, and more regular in their dimen- 

 sions, whilst the non-poriferous side is minutely granular. In 

 B. Trentonensis, on the other hand, the fenestrules are large and 

 irregular, and the non-poriferous side is strongly striated. In the 

 general shape of the frond, it resembles some of the later Fenestellcs, 

 such as F. laxa, but it is clearly not referable to this genus. 



Locality and Formation, — Trenton Limestone, Peterborough, On- 

 tario. Collected by Mr. George Jennings Hinde, F.G.S. 



