440 DR F. A. BATHER. 



C. giganteus Leuchtenb., C. atavus Jaekel, and C. constrictus. The arrangement in 

 C. angidatus Wood is not stated. 



§ 302. In all other species, according to Dr Jaekel (1899, p. 220), all the rhombs are 

 disjunct. But this statement does not agree with his own figure of (7. alter (pi. 11, f. 8), 

 in which rhombs 16-17 and 17-18 are clearly conjunct. 



§ 303. A further specialisation is the multidisjunct structure (text-fig. 46), first 

 observed by Dr Jaekel in his C. interruptus{YS99, pp. 185, 204, 217, 220, pi. 10, f. 9). 

 Here, instead of a single wide bridge along the suture, there are several narrow bridges, 

 between which the folds appear (see § 345, text-fig. 59). 



§ 304. The proximal region of the Stem has been described by Dr Jaekel*(1899, pp. 

 183, 215) as consisting of ring-like columnals of two kinds: a series of larger, outer 

 ossicles, each with an outer collar or flange projecting upwards slightly 

 and to a greater extent downwards, and sometimes enveloping the 

 upper part of the flange below ; a series of smaller, inner ossicles, 

 alternating with the flanged ossicles, and invisible from the exterior 

 except when the stem is strongly bent (text-fig. 47). This descrip- 

 tion is based on stems of which the stereom is preserved. It seems 

 likely to be correct for the Russian species, but it is possible 

 that other species may have a slightly different structure. I am 

 unable to draw clear conclusions from the Girvan material, but ^^^'J^^' ^ ''~ ° \ 



' section 01 the proxi- 



the stem of C. constrictus seems capable of another interpretation mai region of the 



, „ . stem of Cheirocrinus, 



is "^"^Oj. based on Jaekel's 



§ 305. The rather large encrusting roots, and the associated pen- drawing (i899, f. 34) 



_ _ . of a specimen from 



tamerous columnals with very wide lumen, which Dr Jaekel believes the"Giauconitkaik" 

 to have come from the distal region of a Cheirocrinus stem (1899, '■°^ the Baltic pro- 



o V ' vinces ^. 



pp. 183, 215), do not appear to me in the same light. 



^ 306. The median region of the stem has hitherto been either unknown or 

 undescribed. Of C. Logani, E. Billings wrote (1858, p. 58), "the column is short, 

 strongly annulated, and tapering to a point at its lower extremity." At the Chicago 

 Exhibition (1893), however, I noted a specimen from the Trenton Limestone of Trenton 

 Falls, N.Y., in which the stem was rather long and tapering. This region will be found 

 described for C. constrictus (§ 328), and it will be clear that a stem of that nature, at 

 any rate, can have had nothing to do with the fragments described by Dr Jaekel 

 (§ 305). On the contrary, it suggests a continuance of tapering to the distal extremity, 

 and the entire absence of a root. Similarly, the lateral position of the anus with its 

 enlarged periproct suggests that the modification which gave rise to Pleurocystis had 

 already begun, that the animal no longer retained the normally erect pelmatozoic 

 position, at least in adult life, and that, in harmony with this change, it also relinquished 

 its primitive attachment (see further § 607). 



§ 307. The Species of Cheirocrinus — The following arrangement has been pub- 

 lished by Dr Jaekel (1899, pp. 219, 221), but appears to have no general phylogenetic 



