INVERTEBRATES. 311 



plate of moderate size, longer than wide, and projecting some- 

 what above the summit of the first radials ; apparently irregu- 

 larly heptagonal or octagonal in form, with two or three short 

 sides above, for the reception of smaller pieces, and supported 

 upon the short, truncated, upper side of one of the subradial 

 plates, while on either side it connects with the first radials, 

 excepting on the right inferior sloping margin, which rests 

 against a large, oblong, subanal piece. This latter plate is 

 larger than the true anal piece above, and rests between the 

 superior sloping sides of two of the subradial plates; while its 

 upper oblique side supports one of the inferior sloping sides of 

 the first radial on the right of the anal piece. Upper trunca- 

 ted side of the first radial plates, much thickened within, and 

 provided, near its outer margin, with a distinct, longitudinal 

 rig. 31. furrow, inside of which is 



a transversely crenulated 

 ridge, with an indentation 

 in the middle ; inside of 

 this ridge the margin pro- 

 //"-—i i — y t^^^\ jects considerably, curves 

 ^^ v^3 ( a little upwards, and has 



a distinct notch or sinus 



D-o^ 



^ Jv---\ / *^7 * n ^ e m iddle. Height to 



) f \ | / the top of first radial pieces 



L / on the longer side, about 



1 inch; greatest breadth, 



1.38 inches ; breadth of 



base, about 0.67 inch; di- 



Cyathocrinus sangamonensis. (Nat. size) ameter 01 COlUmnar tacet, 



This diagram shows basal, subradial, first radial, and A OK in oh 

 anal pieces. KJ.atf \.u\ji±. 



We are in sortie doubt in regard to the generic relations of this species, not 



having seen any specimens showing the arms, summit, or any of the radial 



«.pieees above the first. It differs from the characteristic species of the genus 



Cyaihocrinus, in having a large, subanal plate intercalated between its subra- 



dials, and one of the first radial pieces. It also differs in having two of its 



