108 INVERTEBRATE PALEONTOLOGY. [WHITE. 



The largest- example in the collection is nearly nine centimeters in 

 length, the calyx having a diameter of twenty-five millimeters; but the 

 average size of nearly one hundred examples is considerably less. 



This species differs from all other species of Amplexus known to me in 

 its zaphrentoid form, but its plain calyx-bottom, its broad transverse plates, 

 and the absence of a vesicular zone, leave no doubt as to the propriety of 

 referring it to the genus Amplexus. 



Position and locality. Lower Aubrey Group; Split Mountain Canon, and 

 near Echo Park, Utah. 



Echinodermata. 



Genus EUPACHYCRINUS Meek and Worthen. 







Eupachycrinus platybasis (sp. nov.). Calyx nearly flat; basal pieces 

 small, concealed by the first joint of the column, which is proportionally 

 large ; subradial pieces rather small or of medium size, their inner ends also 

 covered by the first joint of the column; judging from the portion of them 

 that is visible, they are all of nearly regular rhombic outline; first radials 

 much broader than long, broadly convex from side to side and abruptly 

 convex from within, outward, all of them ending with a regular obtuse angle 

 between the subradial pieces except the left anterior one, the angle of which 

 is made a little irregular by the interposition of the second anal plate ; first 

 anal piece of the same size and shape as the subradial pieces; second anal 

 piece apparently nearly as large as the first, between which and the left 

 anterior first radial piece it is interposed, reaching nearly as far inward as 

 the first radial piece does, and at which point it ends with an acute angle; 

 plates all massive. Remainder of the structure unknown. Sutures all linear > 

 surface nearly or quite smooth. 



Diameter of the calyx, eighteen millimeters. 



This species differs from the typical forms of the genus in the extreme 

 flatness of its calyx, but the arrangement, number, and general character of 

 the pieces composing it leave no doubt as to the propriety of referring it to 

 Eupacliycrinus. 



Position and locality. Lower Aubrey Group; confluence of Grand and 

 Green Rivers, Utah. 



