CANADIAN FOSSILS. 27 



C. SEMICAKINATA, N. Sp. 



Figure 2. 



C. semiuncialis, spird regulariter conicd, nisi suturis horizontalibus insectd ; 

 striis obscuris ; anfractibus 4-5 supra biangulalis, infra 6-carinatis, 

 carind secundd maximd mediand, quartd prominuld ; ore rotundo. 



Of this well-marked form there are only two or three specimens, 

 the largest not above half an inch in height. They were first taken 

 for Pleurotomaria percarinata, Hall, which, as it shews nothing of the 

 characteristic band or notch, may very probably belong to Cyclonema. 

 But in that species the sutural space is not horizontal, and the 

 conical spire seems therefore blunt instead of deeply incised, while 

 the keels below the chief ridge are mostly equal. 



There are two or three other species in the Ottawa limestone, one 

 beautifully ornamented, and like a Pleurotomaria in everything except 

 the notch. 



Locality. — Allumette Islands. Holopea obliqua, Hall, accompanies 

 it. 



Trochonema. 



Under this proposed name will fall several Upper and Lower 

 Silurian species, such as the Turbo trockleatus of McCoy, and Euom- 

 phalus tricinctus of the same author; only those however with the 

 strong concentric ridges possess a wide umbilicus. Inaclms angulatus, 

 Hisinger, is probably an extreme form of the group, with a greatly 

 depressed spire. Pleurotomaria umbilicata, Hall, is the one here 

 described, and the type of the genus. 



T. UMBILICATA, Hall. 



Plate VI. Figure 3. 



Troch. unciam lata, depressa ; anfractibus perangulatis, facie externd latd 

 verticali ; umbilico latissimo, tumido, carind obtusd yermarginato. 



Prof. Hall, Palasnotology of New York, vol. i., plate 10, fig. 9, and 

 pi. 38, fig. 1 ; p. 43-175. 



Turbinate, depressed, the last whorl often free; the spire short, truly 

 conical, interrupted only by the vertical faces of the whorls and the 

 hollow sutural edge. Volutions, 4 or 5, with 4 carinae, of which two 



