632 GEOLOGICAL SURVEY OF IOWA. 



Forbesiocrinus wortheni (n.s). 



PLATE XVII. FIG. 5. 



BOJJY large, somewhat discoid : rays prominent. Basal 

 plates small, slightly projecting beyond the column-area. 

 Subradial plates of medium size. Radial plates large, strong, 

 more than twice as wide as long; the first ones somewhat 

 heptagonal ; the second and third unequally five-sided, by 

 the truncation of one of the upper lateral angles : fourth 

 radials pentagonal, with the apex much extended upwards. 

 Secondary plates three ; those of the third division seven, 

 with the patelloid or intercalated plate conspicuous in the 

 divisions of the ray (although omitted in the figure). Inter- 

 radial plates thirty or more. Anal plates about twenty de- 

 terminable (the full number unknown). Interaxillary plates 

 eight, ten or more : interaxillaries of the third division 

 three, four or more. Surface finely granulose. 



This large and fine species differs conspicuously from any of the other forms in 

 its great number of interradial and interaxillary plates, as well as in the form and 

 proportion of the plates of the rays and their subdivisions. 



Fig. 5. Basal view of the specimen, as it lies expanded on the surface of the stone. 



Geological formation and locality. In the Keokuk limestone : Keokuk, 

 Iowa. 



Forbesiocrinus whitfieldi (n.s.). 



BODY subdiscoid : rays depressed. Basal plates minute, 

 presenting five low angular elevations above the narrow basal 

 ring, with three suture-lines. Subradial plates large ; four of 

 them pentagonal and one hexagonal. Radial plates twice as 

 wide as long ; the lower ones pentagonal, the second and 

 third hexagonal, and the fourth pentagonal. The secondary 

 or supraradial plates two on each subdivision, where the 

 second bifurcation occurs : plates of the third division three. 

 Interradial plates ten ; interaxillary plate one : anal plates 

 unknown. Plates scarcely indented on their upper margins. 



