IQI5] - PaLaEozoic Fossits rRoM Hupson Bay. 37 
The development of the septa in this species suggests an inter- 
mediate position between Zaphrentis and Amplexus: on this account I 
decided in the preliminary report to erect a new genus, Tyrellia, for its 
reception. Further consideration, however, has induced me to place 
the form under Amplexus. According to the definition of the two 
genera given by Milne-Edwards and Haime, our specimen is a Zaph- 
ventts when young and an Amplexus when old, because in the younger 
stages the septa meet at the centre of the tabule and in older stages 
they ‘‘do not extend to the centre of the visceral chamber and leave 
the upper surface of the tabula naked and smooth in that part”. It 
was on this account that I proposed to create a new genus. Lambe, 
however, defines Amplexus as differing from Zaphrentis ‘‘only in the 
feeble development of the septa’’. There is no difficulty in placing the 
form under Amplexus in view of this more generalized definition. I 
am also inclined to this decision by a comparison of our form with the 
figure of Amplexus corallotdes, Sowerby, which appears in Plate XXXVI 
of Milne-Edwards and Haime’s monograph of the British Fossil Corals. 
Locality—Limestone rapids, Severn river, District of Patricia, Ontario. 
Horizon—Silurian. 
No. 300 S. Royal Ontario Museum of Palaeontology. 
Cf. CYSTIPHYLLUM NIAGARENSE, Hall sp. 
CONOPHYLLUM NIAGARENSE, Hail. Pal., N.Y., Vol. II, p. 114, pl. 32, figs. ga-n, 1852. 
CYSTIPHYLLUM HURONENSE, Billings. Cat. Sil. Foss., Anticosti, p. 92, 1866. 
CYSTIPHYLLUM NIAGARENSE, Rominger. Geol. Sur. Mich., Foss. Corals, p. 137, pl. XLIX, 
fig. 3, 1876. 
CyYSTIPHYLLUM NIAGARENSE, Sherzer. Bull. Geol. Soc. Am., Vol. III, p. 266, 1892. 
CYSTIPHYLLUM NIAGARENSE, Lambe. Ottawa Nat., Vol. XII, p. 224, 1899. 
CYSTIPHYLLUM NIAGARENSE, Lambe. Geol. Sur. Can., Cont. to Can. Palaeon., Vol. IV, 
pt. II, p. 190, pl. XVI, fig. 7, 1900. 
The collection contains one small fragment showing the endothecal 
tissue and part of the calyx of a form evidently referable to Cystrphyllum. 
The calyx appears to have been fairly deep, and it shows traces of septa 
on the blistery surface. General shape and size of the corallum not 
determinable. Very doubtfully referred to C. niagarense on account of 
the depth of the calyx. 
Locality—Limestone rapids, Severn river, District of Patricia, Ontario. 
Horizon—Silurian. 
No. 340 S. Royal Ontario Museum of Palaeontology. 
