58 



The last ones are axilliii-y and support, on the upper sloping 

 sides, the tertiary radials. The tertiary radials vary in num- 

 ber in the different rays that are preserved, in our specimen, 

 from four to six, but all the series are not preserved, and 

 hence the variation may be greater. There are only a few 

 plates preserved in tlie quaternary series, so that any defini- 

 tion of them will be of no special service, though the total 

 number of arms is necessarily forty and probably sixty. 



The regular interradial areas arc of unequal size, more or 

 less elongate-ovate and covered witn large plates. All of the 

 areas are not preserved in our specimen, but in tliose pre- 

 served there are from sixteen to twenty plates. Tlie inter- 

 secondary areas are much elongated and have numerous plates. 

 The intertertiary radial areas are also elongated and have three 

 or more plates following each other. In the azygous area an 

 heptagonal plate broadly truncates a subradial. It is followed 

 by two plates in the second range, three in the third, four in 

 the fourth, three in the fifth, three in the sixth, three in the 

 seventh, two in the eighth, two in the ninth, and above the.se 

 they arc not preserved in our specimen, but as these twenty-three 

 plates do not extend as high as the intersecoudary or intei-- 

 tei'Uary plates, it is evident tliat tiie total number will be 

 found to l^e from twenty-seven to thirty. 



This species is distinguished by its rounded massive form, 

 transverse or slightly concave beveled sutures, elongated inter- 

 radial, intersecondary, and intertertiary areas, and by the 

 structure of the azygous area. It will thi-ow no light \ipon it 

 to contrast it with other species, for it can always be distin- 

 guished on the sliglitest observation. 



Pound by Geo. K. Greene, in whose honoi' the spec-ifii- name 

 is given, in the Keokuk Group, at Edwardsvillc Tiiili:in:i, and 

 now in the collection of Win F. R Giirley. 



l'X)KBESOC'RINrS M.\( ADAMSl, 11. sp. 



/'/(//(' r. Fig. 1, (izijgoiis side; Fig. i', opposite view of t lie same 



specimen. 



Species very large. Radial .series })rominent and interradial 

 areas depressed so as to give the calyx a marlvcd (luiiKiuelo 

 bate outline as seen from below. Plates rounded in the radial 



