1916] The Ottawa Naturalist 107 



the Trenton, while Bassler cites Comarocystites punctatus from the 

 Curdsville at Ottawa, in Ontario, Canada. From this it is evident 

 that Bassler correlates at least the lower Trenton horizons at Ottawa 

 with the Curdsville of central Kentucky. The two horizons at which 

 Comarocystites occurs, even if referred to different groups, evidently 

 are not far removed from each other- 



25- Literature on Comarocystites shumardi and obconicus. 

 Comarocystites shumardi, Meek and Worthen. 



Meek and Worthen, Proc. Acad. Nat. Sci., Philadelphia, 

 1865, p. 143. Geol. Surv. Illinois, 3, 1868, p. 292, 

 , fig.; pi. 1, figs, la, b. 



The diagram on page 292 is so drawn as to sug- 

 gest the presence of only three basal plates; in the 

 preparation of this diagram the authors probably 

 were influenced by the original description of 

 Comarocystites punctatus (Canadian Journal, 2, 

 1854. p. 268) in which Billings states that "upon 

 the upper joint of the column stand three low but 

 broad pentagonal plates, with serrated edges 

 above." As a matter of fact- however, these ser- 

 rated edges suggest the presence of more than 

 three basal plates, although the sutures separating 

 these plates are not clearly defined in the type 

 specimen diagrammed- A line drawn vertically 

 through the center of the diagram would be 

 parallel to the transverse apical food-groove of the 

 specimen, the plates on the left side of the theca 

 being indicated at the top of the diagram, and 

 those on the anal side, at the bottom of the dia- 

 gram. At the time the diagram was prepared, the 

 upper part of the left side of the theca was con- 

 cealed bv the matrix- Traces of the transverse 

 apical food-groove, bifurcating at the end, were 

 present on the left side of the top of the theca, but 

 were not recognized by the authors. The specimen 

 has been cleaned by the present writer and re- 

 drawn for this paper. (Text diagram No. 6). 

 Figure la on plate 1 is oriented exactly opposite 

 to the diagram, the anal side facing the top of the 

 figure and the left side facing the bottom. Figure 

 lb presents the right or anal side of the specimen; 

 the parts immediately surrounding the anal pyra- 

 mid and all of the upper left hand part of the 

 theca is missing, the extreme top of the figure 

 representing the broken edges of that part of the 

 theca which is bevond the break. 



