THE OTTAWA NATURALIST 



Vol. XXVI. JUNE-JULY, 1912 Nos. 3 and 4 



ON TWO NEW CRINOIDS FROM THE TRENTON 

 FORMATION OF ONTARIO. 



(Plate IV, Figures 1-4). 



By W. A. Parks and F. J. Alcock, University of Toronto. 



In his recent memoir on Trenton Eehinoderms prepared 

 for the Geological Survey of Canada, Mr. Frank Springer refers 

 to a specimen in the museum of the University of Toronto as 

 a new species of Carabocrinus* This opinion was expressed 

 in confirmation of a diagnosis by the writers which was based 

 on the character of the arms alone. A careful cleaning of the 

 specimen has revealed the cup in a fair state of preservation but 

 insufficiently perfect to warrant conclusions as to certain of 

 the plates. Despite this imperfection, it is highly probable 

 that the specimen represents a new genus of the Inadunate 

 Monocyclic Crinoids referable to the family Heterocrinidae. 



The cup. The cup is about 15 mm. high and 17 mm. 

 wide. Five pentagonal and approximately equal basals are 

 presented. The plates of the radial ring differ greatly from one 

 another: three of them are large with a facet extending across 

 the middle third for the insertion of the arms. The other two 

 radials are transverselv divided and do not appear to bear arms 

 of the same character as those arising from the larger plates. 

 Owing to the crushed condition of the specimen it is impossible 

 to be sure of the other points in the anatomy of the cup, but it 

 would appear that one of the large radials is somewhat greater 

 than either of the others and that its upper left corner is trunc- 

 ated for the insertion of a small anal. In the drawing (plate IV, 

 fig. 1), the right-hand dotted line represents the uncertain suture 

 between the supposed anal and the contiguous large radial. 

 The middle dotted line is almost certainly a suture and the 

 lefthand dotted line is, in all probability, due to a crack across 

 the superradial. The dissection shown in fig. 4 is drawn on the 

 assumption that the small triangular plate is a true anal. If 

 this conclusion is correct, then the large radial is the right pos- 

 terior and the divided plates are the left posterior and the 



*Geol. Sur. Can*., Memoir IS P., Ottawa, 1911. 



