NOTES ON HAMILTON SPECIES 167 



crinal limestone of the Thedford region. Whiteaves mentions collecting 

 at Thedford a few specimens without stating the precise horizon. The 

 species is common in and just below the •Encrinal limestone of western 

 New York, and is also found in the lowest true Hamilton beds of that 

 region. On the other hand, it is unknown below the Encrinal in the 

 Genesee valley, but common above it. This indicates an eastward 

 migration.* It is not impossible that the species exists in beds below 

 those exposed at Thedford. 



Notes on some of the Hamilton Species from Thedford and 



VlCTNITY 



CERATOPORA INTERMEDIA (NICHOLSON) AND C. NOBILIS [NICHOLSON) 



An examination of sections and silicified specimens of Nicholson's 

 Syringopora intermedia from the type locality at Thedford proves this to 

 belong to the genus Ceratopora denned by Grabau in 1899. A larger 

 species of the same genus occurring with this, but in less abundance, 

 has been identified with Nicholson's Syringopora nobilis. 



These corals characterize the upper calcareous beds of the exposed sec- 

 tions at Thedford and Rock glen, where they are not infrequently silici- 

 fied. C. intermedia also occurs in the coral layer. 



HELIOPHYLLUM HALLI E. AND H. 



In his recent monograph on the corals of Ontario, Lambe refers the 

 species of Heliophyllum to Cyathophyllum, discontinuing the genus.f 

 He gives no reason for this, and we can only gather that he does not 

 consider the presence of carinse a sufficient characteristic for generic 

 differentiation. 



A number of sections of characteristic specimens of Heliophyllum halli 

 E. and H. from the coral layer of Thedford and vicinity have shown 

 that in its young stages H. halli has the characters of a Cyathophyllum, 

 the septa being without carinse. The age of appearance of carinse varies 

 in different individuals, according to the degree of acceleration which 

 they have experienced in their development. A cross-section of a young 

 individual, measuring 30 millimeters across the calyx, and well supplied 

 with carinse, was made about 12 millimeters below the calyx, where the 

 diameter was from 12 to 15 millimeters. It shows no carinas whatever. 

 The principal septa unite near the center, and the interseptal loculi are 

 well supplied with dissepiments, indicating vesicular tissue. The speci- 

 men is a rapidly expanding one, and the number of carinse on each 



♦Grabau (1), 1898, p. 329. 



f Contributions to Canadian Paleontology, sec. 4, pt. ii, 1901. 



