REPORT ON THE CRINOIDEA. 



331 



1878. Pentacrinns MiiUeri, Agassiz, Bull. Mns. Comp. Zool., vol. v., No. 6, p. 56. 



1879. Pentacrinus Mulleri, Pourtalis, Bull. Mus. Comp. Zool., vol. v., No. 9, p. 214. 

 1879. Pentacrinus Mulleri, Agassiz, Bull. Mus. Comp. Zocil., vol. v., No. 14, p. 296. 

 1882. Pentacrinus decorus, P. H. Carpenter, Bull. Mus. Comp. Zool., vol. .\., No. 4, p. 171. 



Dimensions. 



Greatest lengtli of stem, to fiftietli nodo, 



Diameter of stem. 



Longest cirrus (thirty-two joints). 



Diameter of calyx, . 



Diameter of disk. 



Length of arm (one hundred joints). 



Length of distichal pinnule (thirteen joints). 



Length of pinnule from lower third of- arm (twenty joints), 



80 '00 cm. 



4-75 mm. 

 27-00 



8-00 

 12-30 

 80-00 

 13 00 

 16-00 



Stem moderately slender aud usually smooth, with a rounded pentagonal outline. 

 Seven to sixteen (usually eleven or twelve) internodal joints, with much erenulated 

 edo-es. Nodal joints somewhat enlarged, expanding from above downwards to the top 

 of the cuTus -sockets. These are deeply hollowed, and have a pear-shaped form, being 

 continued- downwards as well marked grooves on to the infra-nodiils. Cirri small and 

 slender, rarely composed of more than thirty joints, the first six of which are Cjuite short 

 and the remainder squarish or slightly elongated^ with a moderately smooth dorsal edge. 

 Terminal claw small, with no opposing spine. Lowest limit of the interarticular pores 

 between the ninth and eleventh nodes. 



Basals very variable, sometimes quite small, inconspicuous, and isolated ; but 

 presenting all gxadations from this condition up to that of large triangular knobs 

 standing out prominently from the general plane of the calyx, and meeting one another 

 by their extended lateral angles. 



The two outer radials united by bifascial articulation. The rays and their sub- 

 divisions sometimes separated by plated perisome, and sometimes in close apposition ; 

 but the sides of the lower arm-joints are scarcely flattened at all. Ten to twenty -five 

 arms. Primaries of two to seven distichal joints. When three or more distichals are 

 present the first two are united l>y l)ifascial articulation, th^e second bearing a pinnule, 

 while the third or sometimes the axillary is a syzygy. But if there be only two 

 distichals, and the axillary be a syzygy, the first bears a pinnule and is united to the 

 second by muscles. Lastly, if the axillary be not a syzygy, there is a bifascial articula- 

 tion between it and the first distichal. Secondary arms (when present) of one to nine 

 palmar joints, which vary in character as in the primary arms, though to an even 

 greater extent. If the arms l^ecome free at the radial axillary the first syzygy is usually 

 on the third brachial ; but if the primary arms divide there is generally a syzj-gj^ in the 

 second free brachial, though not unfrequently it occurs between the first and second. The 



