TAXOCRINIDAE 401 



The roughened or closely studded surface of the stem below the contraction is unique, 

 at least among the Paleozoic crinoids ; as ordinarily found it looks like an irregular marking 

 which was at first supposed to be the work of parasites, but careful cleaning of the specimens 

 brought out a certain regular arrangement of peripheral beads into whorls, at various inter- 

 vals, which suggested that the intervals between them might be the sockets for cirri. In the 

 magnificent specimen shown by Plate LVI, figures 3a, b, the stem is complete and in place, 

 though separated in the drawing for convenience ; it shows the sculpturing very plainly for 

 about three-fourths of its length, with the toothed whorls very close together but altogether 

 too irregular for any connection with cirri ; below this part the enlarged nodal columnals 

 appear quite regular, and from several of them the stumps of strong single cirri are seen 

 projecting, but with no indication of any others constituting a whorl. The structure is doubt- 

 less nothing more than a bead-like peripheral ornamentation of the columnals, such as are 

 shown upon stems of Millericrinus (DeLoriol, Crin. de la Suissee, pis. 12, 21. The 

 stem of a maximum specimen is about 20 inches long, indicating a quiet, fairly deep-water 

 habitat. 



This species is a thoroughly characteristic example of the genus as I understand it, and 

 by reason of the number of individuals and their excellent preservation lends itself especially 

 well both to statistical examination of its general characters, and to the study of structural 

 details. I have upwards of 200 specimens, nearly half of them free from the matrix, and 

 with all or nearly all their rays intact. Upon these I have tabulated the data as to the number 

 of brachials in the first and second divisions of the rays, with the following result : 



In 93 specimens having 444 rays exposed, only 6 show any departure from the normal 

 number of 3 primibrachs, these having less than 3 in 19 rays.; thus the generic character 

 holds good for this strong species with a variation of less than five per cent. In the 887 

 rami showing the secundibrachs 516 have 3 IIBr, and 371 have 4 or more; while therefore 

 the shorter habitus predominates, it is only to the extent of about 58 per cent of the whole ; 

 so that the species must be considered variable in this character. The increase of inter- 

 brachial plates with growth of the individual is shown by the series of specimens on 

 Plate LVI. Some authors with sufficient literary energy would have made several species 

 out of them on this character. 



The preparations illustrated on Plate LVII show in the greatest detail the essential struc- 

 tures which characterize the genus, and to a greater or less degree the family : 



(1) The Posterior Basal. We have this in almost every condition of exposure to bring 

 out the special fact concerning it, that it is not suturally united to succeeding plates at its 

 distal margin, but supports the anal tube in a rounded socket well down upon its outer, or 

 dorsal, surface ; figures 5 and 6a show it with the lower plates of the tube in place, the border- 

 ing perisome intact on the right side, and the left posterior ray removed. In 6a the remnants 

 of the thin and fragile ventral perisome are seen, being as much of it as has ever been found 

 in this species. In this specimen part of the right posterior ray is removed, and the inner 

 side of it is shown at 6b, where the rounded lateral margins next to the anal side and above 

 the interbrachials on the other side may be seen, with the slight linear depression marking 

 the attachment of perisome ; 6c is the left posterior ray of the same specimen, disarticulated 

 at the basi-radial suture, and posed so as to show its left margin, with the sutural faces con- 

 necting with the interbrachials whose apposed faces are seen at the left of 6a; it also shows 

 the inner surface of the ray. On the latter are seen fine longitudinal grooves starting on the 

 secundibrachs, running with several of them parallel for some distance until in the distal 

 part they are replaced by a good-sized median furrow, bordered by small depressions which 

 form the seat of attachment of side or covering pieces. It looks as if these numerous longi- 

 tudinal indentations on the IIBr, IIIBr, anfl partly on IVBr, served also for the attachment 

 of perisome below the base of the free arms, perhaps covering some smaller ramifications of 



