A MONOGRAPH OF THE EXISTING CRINOIDS 79 



complete) are broken. The breadth of the proximal portion of the arms is 1.7 mm. 

 The intersyzygial interval is from 4 to 11 muscular articulations. Pj is 8.2 mm. long 

 with 15 segments. P 2 is 5.8 mm. long with 14 segments. P 3 is 4.8 mm. long with 11 

 segments. P 7 is 3.8 mm. long with 9 segments. 



(5) The 13 arms have full-grown regenerates of brighter color than the proximal 

 portions. This specimen was attached to a sponge. 



(6) The cirri are in 14 columns. They are XV, about 20, about 12 mm. long. 

 The 12 arms are 60 mm. long. P! is about 5 mm. long with 14 segments. P 3 is 2.4 

 mm. long with 8 segments. The distal pinnules are 4.5 mm. long with 12 segments. 

 The disk has coarse granules along the ambulacral furrows. 



(7) The diameter of the centrodorsal is 3.2 mm. The cirri are XV, 21, about 13 

 mm. long. The 18 arms are all broken. The disk is 6.5 mm. in diameter and is plated 

 with coarse granules. 



(8) The cirri are in 15 columns and are XV, 21-22. The 13 +arms (on three post- 

 radial series 3, 3, 3) are 65 mm. long. P] is 6 mm. long with 16 segments. P 2 is 3.3 

 mm. long with 9 segments. P 4 is 2.8 mm. long with 6 segments. 



(9) The cirri are XV, about 20. The 15 arms are 55 mm. long. PI is 6 mm. long 

 with 16 segments. P 2 is 3 mm. long with 9 segments. The distal pinnules are 5 mm. 

 long with 1 1 segments. 



(10) The diameter of the centrodorsal is 2.8 mm. The cirri are XIV, 20-23. 

 The arms are at least 13, 60 mm. long. The diameter of the disk is 4.8 mm. This 

 is a 6-rayed specimen. 



(11 and 12) These specimens are dried; they have 11 and 12 arms. 



Gislen said it seemed to him that with the present limitation of the genera within 

 the Charitometridae one must refer this species (mortenseni) to Monachometra. The 

 only species previously referred to this genus, M. fragilis, differs sharply from M. 

 mortenseni. He noted I had informed him that the opposing spine is double in M. 

 fragilis, as in Diodontomelra. From this genus it is distinguished by the totally 

 different appearance of the centrodorsal. Monachometra mortenseni has a simple 

 opposing spine, and besides dorsal spines, which are absent in M. fragilis, other 

 differences are: In M. mortenseni the cirri are XV, about 20, about 13 mm. long, 

 whereas in M. fragilis the cirri are XXX, 17-18, from 30 to 35 mm. long. In M. 

 mortenseni the arms are about 15, from 55 to 75 mm. long, not wall-sided, whereas in 

 M. fragilis they are 19, 145 mm. long, and strongly wall-sided. In M. mortenseni 

 PI is 5 mm. long with about 14 segments; P 2 is about 3 mm. long with about 10 seg- 

 ments; P 3 is about 3 mm. long with about 8 segments, whereas in M. fragilis PI is 9 mm. 

 long with about 30 segments; P 2 is about 10 mm. long with 25 segments; and P 3 is 

 11 mm. long with 22 segments. The largest and stoutest specimen of M. mortenseni 

 (specimen 4) only slightly surpasses these figures. In the Uppsala Museum there 

 is a specimen of M. fragilis which has permitted direct comparison; it has 20 arms 

 130 mm. long. 



Gislen added that the two species of the genus Monachometra are surely not closely 

 related. Nevertheless they must be provisionally ranged in the same genus which 

 will, perhaps, not be possible in the future, as the classification of the Charitometridae 

 is still not completely satisfactory. 



