20 



fibout (ho same size. It is followed by three laryc plates and 

 above these there are either one or two plates, that extend to the 

 top of the calyx aud connect with the plates of the vault. 



This species is distinguished by its general form, depressed in- 

 terradial areas, lobed extention at the arm bases, by the plates of 

 the azygous and regular areas, and otherwise. It is a typical Ki-ci- 

 mocriiiKS and the question now arises whether or not it can be 

 distinguished from Bahcrhius. The expanded basal plates is cer- 

 tainly not a generic character in Aciinocrinus or Baiocrinus, it is 

 not peculiar to Ercimocrinns. Can it be, that taken in connection 

 with the coarse aud expanded arms, it becomes of generic value ? 

 We think not. The column is larger than is usual in Baiocrinus, 

 but that is certainly not a generic character. The form of the 

 calyx and arrangement of the plates is the same as in Balocrimis. 

 The only distinguishing difference left between Ereimocrinus and 

 Baiocrinns is to be found in the expansion of the arms. We be- 

 lieve that, in no instance, can this be of generic importance and, 

 therefore, think that Ereimocrinus is separated from Baciocrinus 

 by specific differences oidy. A mere combination of specific dif- 

 ferences, which, if applied to its full extent, to Baiocrinus, would 

 subdivide tlie genus into many genera. We have, however, i-e- 

 tained the naipe Ercimocrimm, from deference to the opinion of 

 others, and provisionally, because it may be a convenient division 

 of Baiocrinus. 



Found in the Keokuk Group, at Crawfordsville, Indiana, and 

 now in the collection of \Vm. F. E. Gurley. 



AGAKICOCRINUS I'ROFUXDUS, n. sp. 



ri((h' ■'!, Fiij. 1, Ixtsal i'icw: Fif/. 2, summit view; Fi(j. 3, azyrjous 

 (•(>'«! of a suiallcr specimen. 



Sl)ecies large and ])reserving all the characters ascribed to it in 

 numerous specimens. Calyx deep, hemispherical, outline snbpen- 

 tagonal. Plates within the concavity below the third radials, plane 

 and smooth, and tliose from the third radials outward very tumid. 

 The abrupt change from plane to tiunid plates forms a rim within 

 the concavity. 



]>asals small and entirely hidden by the column. First primary 

 radials large, length about e;]ualing the greatest width, a small 

 part abruptly bent into tlie columnar concavity, three hexagonal 

 two heptngonal. Secoiul primary radials large and nearly square. 

 Third primary radials larger than the second and about as large 

 as the first, very tumid, i^eutagonul, axillary, aud in three of the 



