Blastoidocrinus carchariaedens Billings (sp.) 

 Page 97 



Figures a-j are views of outer surfaces of deltoids of different ages ; a-d show 

 only vertical, foldlike ridges; f— j increasing differentiation of surface 

 markings due to additional areas added at the border; in "i" the earlier 

 deltoid has come to lie in a margin composed of apparent folds which lie 

 at right angles to the lateral edges of the plate; in "j" these lateral ridges 

 are even better developed. 



Figure h is unique in its surface markings and figure e in its angles. 



Figure j shows clearly the incised hydrospire exits where the margin of the 

 plate meets the displaced bibrachial. For the corresponding grooves on 

 the bibrachial see the lower edge of figure n on plate 4. 



Figures k-o show the inner surfaces of five plates of different ages. There 

 has been no widening of the hydrospire grooves with age. Figure 

 n shows traces of the thin sheets of the hydrospires themselves. 



The specimen represented at j is the property of Mr Percy E. Raymond. 

 The other specimens figured are now in the New York State Museum. 



It may be noted that the hydrospire exits are less in number than the 

 hydrospire folds that feed them. Two or three folds occasionally empty 

 through one exit. There is evidence of partial or incipient anastomosis 

 along the line of hydrospire origin. 



