55 



seven plates. There is one rather Large plate, followed by 

 either one or two ranges of two plates each, and above these 

 there are two or three plates, one above the other. There are 

 no intertertiary radials. In the azygous area two plates trun- 

 cal ■ a subradial, which is more than twice as large as either 

 of the other subradials. There are three plates in the second 

 range, four in the third range, which is at the widest part of 

 the area. Above the third range the plates are irregular in 

 size and not placed in ranges, and number about twelve, the 

 last one of which reaches to the second tertiary radials. The 

 whole number is about twenty-one. 



This species most resembles F. sjieciosus from the same 

 locality; but, while this species is larger, it has not as many 

 regular interradials, fewer secondary radials. and no interterti- 

 ary radials. The azygous areas are altogether different, and 

 so also are the subradials, at the base of the areas. This 

 species has sixty arms, while that species was described as 

 having only forty. The transverse sutures, too. in that species, 

 are much more arcuate than in this. The two species cannot 

 be mistaken for each other. 



Found in the Keokuk Group, in Washington County. Indiana. 

 and now in the collection of Win. F. E. Gurley. 



forbesocrinus MfLTiBRACHiATCS, Lyon & Casseday. 



Plate IV, Fig. 1, diagrammatic view, copied from Sidney S. 

 Lyon's original drawing, by his son, Victor W. Lyon. 



This species was not illustrated by the founders of it, though 

 some drawings of it were made, and, as a natural consequence. 

 other species have I n confounded with it. The errors aris- 

 ing from the want of illustration evidences the imperative 

 necessity of disregarding all definitions of species that are not 

 accompanied with illustrations, where a later author has pro- 

 perly described and illustrated them. Where, however, as in 

 this case, no one has made a synonyn, it is eminently proper 

 to illustrate the species, so that it may stand, as of the date 

 of the publication, in the American Journal of Science and 

 Arts, I'd Ser., Vol XXVIII, p. 235, in 1858. Sidney S. Lyon 

 and S. A. Casseday wrote very full and accurate descriptions, 

 and, for this further reason, it affords us pleasure to be able 

 to furnish an authentic illustration of tins species. It is very 

 doubtful about there beiny any generic distinction be- 

 tween Forbesocrinus and Taxocrinus, and, hence, we find 



