1908] Hybocystis in Ontario 235 



furrow on the arm-bearing radials, nor can such a depression 

 be made out on the external aspect of the arms themselves. 

 In the specimen one arm is lost, two joints of the second are 

 preserved and three of the third. It can not be stated, however, 

 that the arms were complete in three segments. Each arm- 

 joint is much longer than wide and in this differs from H. 

 prohlemaiicus where they are roughly quadrangular. Whether 

 or not the ambulacra were extended on the external face of 

 the arms can not be stated, but it is certain that no trace of 

 such an arrangement is exhibited by the specimen. All the 

 plates of the calyx are pitted but this appearance is probably 

 of accidental rather than of organic origin. 



Locality. ^Township of El don, Victoria County, Ont.. J 

 Townsend, collector. Type, No. 566 T. University of Toronto 

 Museum. 



Remarks. One cannot fail to be impressed with the 

 strong resemblance of Hybocystis problematicus and of H. 

 eldonensis to Hyhocrinits conicus. Bill, and H. tumidtis. Bill, 

 respectively. The resemblance of Hybocystis eldonensis to 

 Hybocriniis pristinus is also remarkable; it may be that the 

 new species is comparable with H. pristinus and the two stouter 

 undescribed specimens more closely related to H. tumidus. 

 The exact similarity in the plates of the calyx has already 

 been established; to this must now be added the close agree- 

 ment in the structure of the anal apparatus. It is significant 

 also that the recent discoveries should have been made in, 

 or near, the same locality from which Billings obtained his 

 tvpes of Hybocrinvis. Wetherby has suggested that a sexual 

 difference mav be all that divides the two genera; in view 

 of the facts above cited this explanation is worthy of especial 

 consideration. One strong objection urged by Wachsmuth 

 and Springer against Carpenter's decision that these fonns 

 should be placed txnder the Blastoidea, is that the calycine 

 ambulacra extend over the basal plates. In the case of the 

 new species this objection does not hold; further, the large 

 pads under the ambulacra show some slight evidence of being 

 separate calcifications. If this latter fact could be estabUshed 

 the radials would become typical "forked plates" of the 

 Blastoids and the pad itself develop into the "lancet plate." 

 While not inclining to this view, the writer thinks it just to 

 Carpenter's conclusions to draw attention to the above facts^._ 



Explanation of Plate. oN* - / " 



Hybocystis problematicus. "^ /^^' ^* ^^\^ 



Fig. 1. ^Tegminal view with arms removed. / /* -^^#-^, <\ ^\ 



O 



