UmTACRINUS : ITS STRUCTURE AXD RELATIONS. 41 



remarkable that the color of this tube should be so different from that of 

 the disk, out of which it seems to rise ; and yet while the disk is of a bright 

 jet, shining like coal, the tube is of a purplish color, light at the base, grow- 

 ing darker towards the extremity, which is often quite dark, but totally dis- 

 tinct from the inky blackness of the disk. The spicules composing the tube 

 lie in close contact, and are apparently not so porous. In specimen No. 71 

 (PI. IV., Fig. 2), where the tube is curled upon itself and flattened upon the 

 disk, these differences in color are distinctly observable. The tube is vari- 

 able in size, probably owing to the greater or less distension of the gut at 

 the death of the animal. It is found in the fossil state in almost every con- 

 ceivable position. An excellent representation of these variations is given 

 on Plate IV. 



In specimen No. 75 (PI. IV., Fig. 1 ; and PI. VII , Fig. 1), the tegmen is 

 in its natural position, the Crinoid having settled disk downward into the 

 soft mud, and thus been compressed vertically ; the tube lies flat, stretched 

 out upon the disk to its full length, the tip extending a little beyond the 

 margin of the disk. The shape of the calcareous plates or granules, both in 

 the disk and tube, and the contrasts in depth of color, are beautifully shown 

 in this specimen. The tube is 18 mm. in height. 



In No. 71 (PI. IV., Fig 2), which is also vertically compressed, the tube 

 is twisted and crushed upon itself, and entirely flattened, with its dark tip 

 lying in the middle, where it looks more like a depression than a projection. 



In No. 76 (PI. IV., Fig. 3), a moderately large individual, with calyx 

 about 47 mm. wide, and compressed between a lateral and vertical position, 

 the tube rises above the level of the free arm branches to a height of 15 

 mm. In a number of other specimens which were laterall}' compressed, the 

 tube is seen in its natural position rising between the arm bases. 



In No. 148 (PI. IV., Fig. 4) the black disk has been itself forced upward 

 by the lateral compression of the calyx, and appears as a conical elevation, 

 which has been exposed by breaking away some of the arms. Surmounting 

 this the purple, funnel-shaped tube, which is very large in this specimen, 

 rises to a height of about 19 mm., its distal end being about the height of 

 the 28th secundibrach.* It is 12 mm. wide at the bottom. Allowing for 



* It will be noted that I do not use the same terms for these and other plates in the brachial series 

 which were employed by Waclismuth and Springer in tlie Monograph of the Crinoidea Camerata. I adopt 

 instead, and sliall hereafter use, the nomenclature and symbols for these parts proposed by Mr. Bather in 

 Lankester's Zoology, Chap. XI., p. 143, and previous papers, as being the most philosophical and accurate, 

 and being also the logical consequence of our own researches. When in 18S1 (Revision, Ft. II., p. 10) 



