﻿scare iikki'I SILURIC AND DEVONIC CYSTIDEA 221 



smaller diagonal which gives them the appearance of Venetian blinds, 



from which its specific name. 



"The pelvis is circular with four reentering angles, composed of 

 four [basal] plates, three of which are pentagonal, and one. having 

 its superior angle truncated, is hexagonal. The lower part of the 

 pelvis terminates externally in a more or less projecting edge and 

 then the plates turning immediately inwards form the sides of a 

 [deep] circular excavation in which the column was instiled. 



" The first [second] series of plates is composed of five; four are 

 hexagonal, and one having upon its lower margin one [i. e., one-half] 

 of the poriferous rhombs is rendered thereby irregular. They are- 

 placed in the four reentering angles of the pelvis; the fifth plate is 

 quadrilateral and rests upon the hexagonal pelvic plate, the superior 

 of which surrounding partly the oral aperture [anus] is also thereby 

 rendered irregular. 



" The second [third] series is composed of five hexagonal plates 

 of which three are rendered irregular by two poriferous rhombs and 

 by the oral aperture [anus]. This oral aperture is large and circular. 

 ( hie of the poriferous rhombs, on the quarter section on the left of 

 the oral aperture, occupies about one-half of an hexagonal plate ; 

 above this rhomb is an elevation, running transversely and having on 

 its summit a furrow [the madreporite] , and below it a single pore 

 [the hydropore], neither of which penetrates through or deeply into 

 the plate. The second poriferous rhomb is on the quarter section on 

 the right of the oral aperture ; it occupies the upper part of the third 

 hexagonal plate, which is thus also rendered irregular. 



the National Museum authorities to Troost's manuscript and fossils still re- 

 maining at Albany, and finally, in the month of November, 1898, the acting 

 administrator of the Hall estate returned to Washington 294 specimens and 

 the manuscript and drawings for 107 species. The specimens for 17 species 

 are still missing. In the Annual Report of the National Museum for 1899, 

 p. 39, is the following statement : 



" As a matter of historical interest, it may be noted that the Troost collec- 

 tion of crinoidea, which, together with the manuscript describing them and 

 drawings for 107 species, was sent by the Smithsonian Institution to Professor 

 James Hall in 1855, was returned last November by the administrator of the 

 Hall estate." 



With very little revision, this work could well have been published in 1850, 

 and most of Troost's species would have been saved to him. However, as it 

 was and still is the custom of the Smithsonian Institution to refer all manu- 

 scripts submitted for publication to a committee of specialists for advice, it 

 is very unfortunate that the work was thus allowed to fall into neglect. Since 

 1850 most of the species have been described, mainly by Hall, but what are 

 left of new species will in the near future lie revived. The blastoids have 

 recently been reworked by Hambach (Trans. St. Louis .lead. Sci., 1904), and 

 the only cystid is described in this paper. 



