33 



Tin's species mi.ulit he rel'ern'il lo , l(7///orT/;//f.s-. ;is it is (ibout on 

 the (liviiliiiji: line between tluit f^etiiis mid SfcudiiocriiiKs. Tlie posi- 

 tion of the plates ])reserve(l iiidifatcs thill the arms were rigid and 

 directed liori/.ontallv. and it is for that reason alone that we refer it. 

 to the latter eeims. 



I'^onnd liy li. A. Ulair in the iini'linglon (Iroiip. near Sharon, in 

 sonthwestcrii Missouri, and now in the collection of 8. A. Miller. 



sTictiAN'ocinNrs Ai.iiiinsi. n. sp. 



I'lulf 1 1. Jii/. i:i. ((li/(/()ll!< si(lc;Jiii. 11. i>l)ii(if<ltc I'icir : Jiij. l.'i. siiiiuiiil 

 rii'ir: J'kj. l(j. Intsiil ricir. 



Species rnedinm or helow medium size. Calyx ob|)yramidal. mod- 

 I'rately truncati'd. pentagonal as seen froiu above or billow. Plates 

 thick, radiately sculptured, and the larger ones bear central nodes. 



Basals form a short, sculptured, hexagonal cup. notched at the 

 sutures and having an hemispherical depression for the attachment 

 of the column. First ])riniary radials very large, about as wide as 

 long, three hexagonal, two heptagonal. Second jirimary radials less 

 than half as large as the first, ratlier wider than long, hexagonal. 

 Third primary radials smaller than the second, pentagonal, axillary, 

 and support on each upper sloping side a single secondary radial, 

 which is axillary, and beyond which the plates are not presei-ved in 

 our specimen. There are twenty ambulacra] openings to the vault. 



The interradial areas all graduate up into the vault and over the 

 andiulacral channels so as to leave no tlividing line between the \ault 

 and the calyx. The regular interradial areas are not uniform. The 

 first plate is followed, in each area, by two plates in the second range, 

 wiiich connect with tlie plates covering tlie sides of the ambulacral 

 channels and with the plates of the vault. In the azygous area the 

 first plate is in line witli the first primary radials, but somewhat 

 smaller. It is followed by two plates in tlu' second range and these 

 by four in the thinl range that unite with the ])lates of the vault and 

 those covering the andiulacral channels. 



The vault is only slightly convex and bears a central jiroboscis. 

 It is covered with convex and nodose polygonal j)lates. 



This species is distinguished from >S'. :^liiirniicHsis by tlii' character 



of the surface ornamentation, by having ])roportionally larger plates 



and fewer plates in the azygous and regular interradial areas. It is 



very clearly a true Slcnanocriiius. 

 — 5 



