﻿222 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 4/ 



" The summit, which has no aperture, as in other species of this 

 genus, may have been composed of five plates. But our fossil, which 

 is very perfect, without the least erosion, being around the sum- 

 mit much complicated by the [ambulacral open] furrows mentioned 

 above, which here combine, the joints of the plates being thereby 

 obliterated, their number and form can not be ascertained. 



" I can say nothing about the column. — the place where I found 

 my specimen contained numerous fragments of different crinoids. 

 The place of insertion of the column is very large in proportion to 

 the size of -the body, its diameter being 4 mm., while the largest 

 diameter of the body is 10 mm. and the length 14 mm. The column 

 was not inserted as is generally the case with crinoids. The cavity 

 is formed of an inclined slope or bevel of about 2 mm., having no 

 articulating striae. 



" I found this interesting fossil in Decatur county, Tennessee, 

 associated with Calymene Blumenbachii [= C. niagarensis] , Ortho- 

 ceratites, Tereb. wilsoni [= IWilsonia saffordi], etc." 



Remarks. — It is interesting to find that Troost had a species of 

 Tetracystis more than 50 years ago, which he then referred to Echino- 

 encrinites. It is closely related to the Manlius T. chrysalis, but 

 differs in being smaller, more circular in transverse outline, and not 

 flattened as is that species; the pectinirhombs, also, have far fewer 

 dichopores. In T. fenestrates there are 12 to 17 pores, and in T. 

 chrysalis from 25 to 35. Of brachioles the former has from 7 to 8 

 on each side of an ambulacrum, while the latter species has 11 in the 

 same space. Plate 19 and deltoid 24 may not be present in T. fene- 

 strates; if they are, they are now obscured by the ambulacralia. 

 However, as Troost's species is otherwise closely related to T. 

 chrysalis, it is probable that other specimens may reveal these two 

 small plates. 



Formation and locality.— The horizon in Decatur county, Ten- 

 nessee, furnishing this fossil, appears to be the Brownsport lime- 

 stone of Foerste, formerly a part of Safford's Meniscus limestone, in 

 the upper portion of the Xiagaran. 



Cat. number 35,091, U. S. X. M. 



Jaekclocystis Schuchcrt 

 Jaekelocystis S< huchert, Amer. Geol., xxnii, 1903, p. 230. 



Definition. — Apiocystinae with the theca pyriform or globular in 

 outline, rounded oval or 4-sided in transverse section, and composed 

 of i<S plates, which are arranged as follows: 



