560 GEOLOGICAL SURVEY OF IOWA. 



Synbathttcrius woitheui (n. s.). 



PLATE IX. FIG. 9. 



BODY and arms extremely elongate, fusiform, strong, terete 

 towards the summit ; greatest diameter at the junction of 

 the radial and arm-plates. Base appearing as a simple, thick, 

 pentagonal piece. First radial plates spreading. Second radial 

 plates long, contracted towards their summit, the arm-plates 

 resting directly upon their upper edges. Arm-plates of nearly 

 equal breadth and height ; length a little the greater. Sur- 

 face granulate. Column, near the body, composed of alter- 

 nating longer and shorter joints. 



The general form of the base is turbinate, swelling out at 

 the summit of the radial plates, and again contracting above, 

 and, with a slight enlargement in the centre of the arms, 

 tapering above to a rounded extremity. 



The specimen described presents an apparently solid base, and exhibits all the 

 characters of the genus given by its author. 



I have named this remarkably fine species in honor of Mr. WORTHEN, whose re- 

 searches in the Carboniferous rocks of the Mississippi valley have brought to light 

 so many new crinoids and other fossils of these strata. 



Fig. 9. View of the specimen, natural size. 



Geological formation and locality. In the Burlington limestone : Jersey 

 landing, Illinois. 



AGARICOCRINITES (TROOST*, MS.). 



" Generic characters. Pelvis hexagonal, divisible into three 

 " parts. Column cylindrical, with striated articulating sur- 

 " face, and pentapetalous alimentary canal. Costals six, 

 " hexagonal. Scapulars five, pentagonal. Interscapulars seven, 

 " subhexagonal" . 



* In a catalogue of Crinoidese published by Dr. TROOST in the Proceedings of the 

 American Association for the Advancement of Science in 1849, p. 60, we find the name 

 of jlgaricocrinus tuberosus; and the same name has been published elsewhere on the 



