26 Mr. W. H. Baily on a new Pentacrinite 



like thick plates, having a double excavation at their lower ex- 

 tremity, where they articulate with the pentagonal stem ; radial 

 plates five in number, about twice as broad as long ; brachial 

 plates also five, broad and triangular, supporting the rays, 

 which are ten in number, very long, composed of cuneiform 

 alternating articulations, and bifurcating four or more times, 

 every alternate joint of these rays being furnished with a long, 

 slender, eight-jointed pinnule. The column consists of a num- 

 ber of pentagonal joints, of equal length, each united by a cre- 

 nulated margin, and for the greater portion of its length com- 

 paratively smooth, but towards the calyx becoming strongly 

 ridged and beaded across the exterior surface of each angle. At 

 about every eighth joint on each of its five angles a closely-jointed 

 ramule was articulated. 



Dimensions of small specimen. — Length of calyx T \j, diame- 

 ter t 2 q inch. Diameter of column rather less than y 1 ^ inch, 

 Length of rays about 2 inches ; length of column nearly 5 inches 

 (probably much longer when perfect). 



Dimensions of larger specimen. — Length of calyx fo, diameter 

 2% inch. Diameter of largest fragments of column y% inch ; 

 other portions vary in diameter from rather less than —^ to 

 T %inch. 



Remarks. — This Pentaerinus is remarkable for its graceful 

 form, which it owes to the slender stem and great propor- 

 tionate length of its arms ; the calyx, like that of the typical and 

 recent example of this genus (Pentaerinus caput- Medusa) is 

 small, and composed of but few plates, the basal series or pelvis 

 consisting of five very convex and solid elements, the lower por- 

 tion of each being excavated to form an articulating surface, 

 which rests securely upon the pentagonal stem ; to these are 

 closely fitted the five radial plates; upon them rest the five 

 triangular brachial plates, the sides of which support the long 

 rays or arms, which bifurcate several times, and are ten in num- 

 ber; commencing from the brachial plate, they continue for 

 about three-tenths of an inch to the first subdivision, consisting 

 of from eight to ten irregularly- shaped joints closely fitting to 

 each other and bearing a second triangular plate, the sides of 

 which, like that of the first brachial plate, support the second 

 division, one branch of which, consisting of fifteen joints, again, 

 bears the third triangular plate, from which springs a third 

 subdivision ; to one of the branches of this division sixteen more 

 joints can be counted without any further branching, the termi- 

 nation of this, the best-preserved of the arms, being still want- 

 ing. The plates composing the rays become flatter and more 

 closely set towards their upper part, their surfaces being marked 

 by a continuous double line or angular ridge (PI. I. fig. 1 A). 



