42<8 SMITHSONIAN INSTITUTION 



were in horizontal position with the rays extended, but always adhering most firmly to the 

 matrix at the ventral side, and had therefore been cleaned with the dorsal side free, as in 

 figure 5 of Plate LXVIII. I took the most promising of these, seventeen in number, bedded 

 them in cement by the dorsal side so they could be manipulated without breaking, and pro- 

 ceeded to remove the matrix from the ventral side and explore the cavity with fine tools. 

 It was a laborious and tedious task, covering several months, which could not be entrusted 

 to another because every stroke had to be watched by the person most interested, so that 

 he might know at first hand what was encountered, and be able to interpret the structures 

 as they were disclosed. 



The first specimen was unproductive (PL LXVIII, fig. 4), showing nothing but the 

 posterior oral standing nearly on end, which as before I did not recognize. The next was 

 figure 7 of Plate LXVII, a medium-sized specimen with rays and calyx unusually widely 

 distended; working inward along one of the rays after uncovering the arms, I discovered 

 the ambulacrum, and then the finely plated perisome ; following carefully with these for 

 a guide, the structures were one by one exposed until the whole appeared as now seen in the 

 figure — a specimen worthy to rank with our celebrated specimen of Taxocrinus intermedins, 

 which first disclosed the real nature of the Flexibilia tegmen as distinguished from that of 

 the other orders. I have given this somewhat minute account because these structures now 

 look very plain and simple in the figures, and it might not be realized from inspecting them 

 that every one of these delicately constructed tegmens was buried in a fine calcareous matrix, . 

 from which it had to be exposed by long and careful work with sharp tools and fine needles, 

 much of it under a magnifier. 



With that of figure 7 for a guide, the other specimens could be exposed with greater 

 confidence, and the structures were afterward found more or less intact in several, as shown 

 by the figures ; some especially clear in one detail and some in another, until they furnished 

 about all the information one could hope to obtain from fossils. In none of the others were 

 the structures so little disturbed as in figure 7, although figure 10 of the same plate, and 

 figure 1 of Plate LXVIII, are almost as good for the general picture. 



Turning now to a more detailed inspection of the figures on Plate LXVII, — figure 7 

 shows the correct relation of the several parts of the tegmen in its entirety ; the strong 

 ambulacra, with their large, elongate, alternating plates, are intact, and the oral pyramid 

 between whose plates they converge to enter the mouth is almost in place ; three of the small 

 triangular, anterior orals, two of which are well seen from the view in which the specimen 

 was photographed for drawing, are apparently exposed almost as they were in life; the 

 fourth is displaced, being pushed in under the one at. the left so that only a small point of it 

 can be seen in the figure. The most striking and unexpected thing about this tegmen is 

 the extraordinarily disproportionate size of the posterior oral. In figure 7 it is nearly three 

 times as large as the area of the other four combined ; it is a relatively huge} triangular or 

 lance-head plate, with the other four orals converging around its blunted apex, at which 

 there is an aperture where they opened out; the posterior ambulacra follow along its sides, 

 and the anal tube, curling to the right, usually lies close to its base or large end. The rear 

 corners are more or less truncated or cut away, and from them a series of large, gradually 

 diminishing buttress-like plates pass to the rear next to the line of the posterior ambulacra ; 

 only one of these is visible in figure 7, the others being broken off ; but they are intact and in 

 position in figures 2a, b, and appear to a greater or less extent in the other figures. 



We have nothing analogous to these in the pliant tegmens of the Recent crinoids, but 

 I suppose them to serve in some way as a support for the large oral. As they appear in 

 these preparations the oral plates seem somewhat irregular in shape ; this is in part due to 

 their accidental positions, especially the large posterior oral which is usually more or less 

 foreshortened ; the smaller ones are found partly imbedded in the debris of the broken down 

 perisome, so that we see them variously exposed and from different angles of view ; also 



