REPORT ON THE CRINOIDEA. 309 



statement concerning Pentacrinus aster ins and Pentacrinus miilleri} He likewise 

 repeated most of his original description of Pentacrinus decorus as a diagnosis of Penta- 

 crinus iniilleri, witli a reference under the latter name to the specimen which he had 

 before him when describing Pentacrinus decorus. He stated that the two outer radials 

 of Pentacrinus astei'ius were united by syzygy, and further added that " the arrange- 

 ment of the joints and the syzygies in the cup is the same in Pentacrinus miilleri as in 

 Pentacyinus asteria, only the syzygy between the second radial and the radial axillary is 

 not so complete." This passage obviously refers to a ligamentous articulation as distin- 

 guished from a true syzygy on the one hand, and from a must;ular joint on the other ; 

 and it is by no means in accordance with Liitken's very positive statements as to the 

 presence of a true syzygy between the two outer radials of Pentacrinus miilleri. Neither 

 does Sir Wj^dlle's description of the nodes as occurring about every twelfth joint agree 

 with Liitken's diagnosis, which records only four to ten internodal joints in Pentacrinus 

 miilleri. As a matter of fact there are eleven or twelve internodal joints in Pentacrinus 

 decorus, and there is no syzygy at all between the two outer radials, but only a bifascial 

 articulation such as occurs in the majority of the Neocrinoidea, and has often been 

 wrongly spoken of as a syzygy, though clearly distinguished from it by Miiller. This is 

 shown in figs. 3 and 6 on PL XXXIV., a copy of which was lettered " Pentacrinus miilleri, 

 Oersted," by Sir- WyvUle Thomson. I cannot Ijut think, however, that if he had lived to 

 w^ork out the " Blake " collection more fully than he was able to do before his health gave 

 way, he would have retained his original views as to the distinctness of his Pentacrinus 

 decorus from Pentaerinus miilleri, Oersted. The result of tliis confusion was that the 

 numerous specimens of Pentacrinus decorus wlaich were dredged by the "Bibb" and the 

 " Blake " in the Gulf Stream and in the Caribbean Sea were referred to Pentacrinus 

 miilleri by Pourtales and Agassiz,^ The two species have really no sort of resemblance 

 to one another, differing in all the characters of the stem, the cirri, the calyx, and the 

 arms. 



The foregoing description is based upon an examination of _^four specimens from the 

 "Blake" collection, two purchased by Sir Wyville Thomson from Mr. Damon, one in the 

 collection of Sir Eawson Rawson, and lastly that in the Museum of the Geological 

 Society of London, which is mentioned by both Miller and Muller as Pentacrinus caput- 

 Medusce. 



Pentacrinus miilleri is readily distinguished from Pentacrinus asterius, which is its 

 nearest ally, by the shortness of the internodes and the modification of the hj^ozygal 

 joints, which, however, is far less marked than in Pentacrinus decorus. The basals 

 generally form a complete ring ; while the lu-anching of the arms is mut-li more regular 



1 Proc. Boy. Soc. Edin., vol. vii. p. TG6 ; and The Depths of the Sea, pp. 434, 435 ; see .also The Atlantic, vol. ii. 

 p. 126. 



2 Bull. Mits. Comp. Zool, vol. i. p. 357 ; Ibid., yol. v. pp. 56 and 214 ; Ibid., vol. vi. p. 296. 



