belonging to the class Radiaria. 319 



an AsteiHas lying on an Echinus ; we think, however, judging 

 from the want of ambulacra, that it would be properly placed 

 among the genera of the Asteriadce : at the same time its vicinity 

 in general form to Say's Family of Blastoidea renders it doubtful 

 whether it ought not to be considered as a connecting link to be 

 placed between the two families of Crinoidea and Blastoidea^ 

 and this suggestion obtains support from the apparently lateral 

 situation of the mouth ; in which respect it resembles some of the 

 Crinoidea. This suggestion, however, involves the following 

 consideration, namely, whether those rays in the Blastoidea^ 

 which by Say are called ambulacrce (a term commonly applied to 

 an apparently corresponding part in the Echinida,) really serve 

 the same purpose ? or whether they be not arms as in the other 

 Crinoidea ? and I venture to assert that there is nothing either in 

 their position or form that militates against such an idea. 



I hope the following description, together with the figure by 

 which it will be accompanied, (Tab XL f. 5.) will serve to give as 

 correct an idea of the fossil in question as can be conveyed with- 

 out the actual examination of the specimen. 



The general form, as far as we can judge from the specimen in 

 which none of the lower part is preserved, is a depressed 

 spheroid ; and it does not appear to have naturally any angular 

 prominences, though owing to the circumstance of its being 

 divided into five sections, it might possibly be very obtusely pen- 

 tagonal. It appears to have consisted of a number of irregular, 

 partly imbricated, crustaceous plates, and its upper half is divided 

 into five sections or compartments, by five equal arms which 

 diverge from the center and are curved all in the same direction. 

 The compartments are not equal in size, in the largest of them 

 and near its center is placed the mouth?; which appears to have 

 been surrounded by two or three rows of very minute, imbricated, 

 crustaceous scales ; the arms, five in number, all diminishing to 

 a point at their outer extremity, and having their upper portion 

 elevated above the body, seem, however, to be attached to it 

 by their under side, and, indeed, partly bedded in it ; each one 

 is divided into two equal parts by a longitudinal groove, and each 

 of these parts is again divided into a number of segments by trans- 



