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blades fill the mortises, and the blades unitj, leaving only a 

 small round opening at the center, which is continued up be- 

 tween the blades, but it is much contracted at the summit. 

 Each arm blade consists of a single plate. The specimen il- 

 lustrated is complete. 



The arm blades are larger and stronger in this species than 

 in P. gorbyi, which is a marked distinction, though the shorter 

 and wider radials will enable any one to distinguish the species, 

 in the absence of the arm blades. 



There are, in the collection of Mrs. J. M. Milligan, five 

 specimens of this species having the arm blades, and many 

 specimens, in which the arm blades are not preserved; there 

 are also specimens, without the arm blades, in the collection 

 of the authors, all of which came from Decatur county, Ten- 

 nessee. It must be apparent to any one having been a stu- 

 dent of the Echinodermata that Pisocrinus is not more nearly 

 related to the order Palcvocrinoidea than it is to the Blasioidea. 

 It has neither the arms nor the vault of a crinoid, besides be- 

 ing anomalous, in the arrangement of the plates of the calyx. 



Pound by Mrs. J. M. Milligan, in the Niagara Group, of 

 Decatur county, Tennessee. The specific name is intended as 

 a compliment to the lady who collected the fossils from that 

 locality and has been a student of Natural History for many 

 years. 



THALAMOCRINIDiE, n. fam. 



This family name is proposed to receive the new genus 

 Thalamocrinus and for the present, the family characters must 

 be regarded the same as the generic. 



THALAMOCRINUS, n. gen. 



[Ety, ihalamos a small house or den; krinon lily.] 



Body pear-shaped or more or less fusi form, and covered by 

 three ranges of plates and a small vault. Basals or first cir- 

 cle plates five, equal. Subradials or second circle of plates 

 five. Radials or third circle of plates six. The vault is un- 

 known but supposed to be like the vault of Zophocrinus. Col- 

 umn small. No arms. Type T. ovatits. 



This genus is only referred to the Palaeocrinoidea provision- 

 ally. Probably a new order should be established to include 

 it and Zophocrinus and some other forms that are not very 

 well understood. 

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