6 



distal side, three ser-ondary radials. the last of which is axillary, 

 and on th(\ ])roxiiiial side two secondary radials, the last of 

 wiiich is axillary, and boars -on the distal side two tertiary 

 radials, and on the j)roxinial side three tertiary radials, the last 

 one bein<j axillary, giving to this ray five arms. There are, 

 therefore, thirty- three arms in this species. The arms are com- 

 posed of a double .series of interlocking plates that are deeper 

 than wide in the lower part, but commence to spread, a1 tlie 

 upper third, and become perfectly flat, in the upper pari, as 

 they do in Erelmocrinus, but without the usual increase in 

 width. Tlie plates of the arms do not seem to lengthen, but 

 instead of closing, so as to have an ambulacral furi'ow on the 

 inner side, they become perfectly flat on both sides, or concave 

 externally. Pinnules dense. 



There are three regular interradials in each area, one large, 

 the other two small, but of unequal length. There are seven 

 azygous interradials, the first one hejjtagonal, in line with the 

 first primary radials, and of about the same size. It is followed 

 by three plates, in the second range, the middle one being the 

 longer and larger one. On each side of the upper part of the 

 middle plate there is a small plate that sepai-ates it from the 

 radial series. Above the middle plate of the second range, 

 there is an elongated plate that extends an angle to the top of 

 the calyx. Tlu; vault is not ex))o.sod, but it bears a long 

 slendei- [ii'oboscis, the end of which is broken o(I at the top 

 of the specimen illustrated. 



This sjnjcic! will bo dislingui.shed by its depressed calyx, and 

 thirty-three arms or seventeen ambulacral oritices, in the vault, 

 and by the llattoning of the arms in the suixu'ior ])art. Tiiis latter 

 character, in a greater degree, possibly, has been regarded as 

 a gcmeric character in Erelmocrinus. This species and others 

 hereinafter described show that the llattoning of the arms is 

 not of generic importance. Many species of Baiocrinus show 

 the tendency of the ai'uis to expand or flatten toward the 

 superior ends. 



Found in the Keokuk Group, at Boonville, Missouri, and now 

 in the collection of S. A Miller. 



