602 E. ETHEEIDGE ON THE PALEONTOLOGY OE THE 



mouth and closely fitting sutures between the whorls distinguish 

 Wiaphistoma from Maclurea. 

 Log. Hayes Point, lat. 79° 42'. 



Genus Helicotoma, Salter, 1856. 

 Helicotoma Kaeesii, Ether. (PI. XXYII. fig. 3.) 



This very discoidal shell is the only representative of what I 

 believe to be the genus Helicotoma. Hall has described (Pal. N". Y. 

 vol. i. p. 9, t. 3) a shell he terms Euomjphalus uniangulatus, which, 

 in some respects, resembles our species, but certainly is not the 

 same. 



8p. char. Shell discoidal, depressed, almost flat, composed of five 

 or six whorls gradually increasing in size, the inner edge of each 

 whorl bevelled on the concave or umbilical side at an angle of 15° ; 

 surface of the shell strongly marked by transverse lines of growth, 

 which arch forward on the sides of the whorls, but are reflected 

 backwards along or near the sutural junctions ; umbilicus open, all 

 the whorls exposed ; a spiral band appears to run along the middle 

 of the whorl ; the aperture not seen, owing to compression ; the spire 

 must have been greatly depressed, probably level with the surface 

 of the shell. 



The genera Euomphalus and Ophileta might well receive our shell ; 

 yet I prefer referring it to Helicotoma ; but its preservation is such 

 as to preclude strict determination. Billings figures a shell which 

 he calls Ophileta? hella (Geol. Canada, Pal. Poss. p. 30, f. 301), which 

 very closely resembles our form ; he refers this to Hall's EuompJialus 

 {Helicotoma) (Ophileta) uniangulatus, but comments upon the flatness 

 and more moderate concavity of the umbilicus. Maclurea crenulata 

 and M. speciosa, Bill., simulate our species, showing how closely 

 allied are these Euomphaloid forms. As before stated, we cannot 

 compare either the entire aperture of Maclurea, or ventral sinus 

 and notch in Ojphileta, on account of the state of preservation ; and 

 our remarks are confined to a single specimen. Both Billings's and 

 Hall's shells occur in the upper part of the Quebec group ; about 

 fifteen species are known on the American continent*. 



Log. Offley Island, lat. 81° 16'. Associated with Pentamerus 

 Copjpingeri, Favosites gothlandicus, Macrocheili, and large Cyrtocerata. 



Genus Holopella, M'Coy, 1855. 



This genus occurs here and there on some of the shelly slabs of 

 Silurian Limestone taken from the cliff-talus and drift at Hayes 



* Meek, in his Eeport on the Geological Survey of Ohio, vol. i. pt. 2 (Palae- 

 ontology), p. 220, t. 19. f. 3, t. 20. f. 1, describes and figures a species of 

 Euompkalus (E. De Cewi, Billings) which much resembles our shell. Billings 

 obtained his from the Corniferous group (Devonian), Co. Haldinand, Canada 

 West ; Meek from Kelley's Island, Lake Erie. Billings described this species 

 in the 'Canadian Journal' (July 1861), p. 358 ; Dev. JFoss. Canada West, p. 94, 

 f. 131, 132, woodcuts. It is the Euompkalus Conradi, Hall, Keport, 1861, p. 107. 



