80 THE VOYAGE OF H.M.S. CHALLENGER. 



semperi and Eudiocrinus japonicus, while in Eudiocrinus varians the first pinnule is on 

 the second brachial. 1 But in his description of Eudiocrinus atlanticus, Perrier 2 says 

 " La premiere syzygie se trouve entre la quatrieme et la cinquieme piece des bras ; c'est 

 la cinquieme qui porte la premiere pinnule ; la place de la premiere syzygie distingue 

 V Eudiocrinus atlanticus de YE. indivisus, Semper ; celle de la premiere pinnule la 

 distingue des trois autres especes." 



In reality, however, the position of the first syzygy and that of the first pinnule in 

 Eudiocrinus atlanticus are exactly the same as in Eudiocrinus semperi and Eudiocrinus 

 japonicus. In describing the fourth brachial of these two species as a syzygy I was 

 using precisely the same terminology as was employed by Muller 3 in his diagnoses of 

 Antedon rosacea, Antedon phalangium, and Antedon eschrichti, when he wrote " Das 

 erste Syzygium befindet sich am dritten Armglied." Perrier however employs a different 

 terminology, which, as I have explained in Part I. and elsewhere, 4 has several disadvantages 

 from a morphological point of view. He describes the fourth and fifth brachials as 

 united by syzygy. It is perfectly true that these are primitively the fourth and fifth 

 joints of the arm, exactly in the same way as the composite third brachial of Antedon 

 rosacea consists of the united third (hypozygal) and fourth (epizygal) joints of the 

 growing arm, as described by Dr. Carpenter. 5 But since the hypozygals of all the 

 brachial syzygies of Eudiocrinus atlanticus, Eudiocrinus semperi, or of Antedon 

 rosacea entirely lose their individuality as arm-joints, bearing no pinnules and taking 

 no part in the movements of the arm, I believe that it is more correct for descriptive 

 purposes to follow Muller and to consider the compound or syzygial joint as one arm- 

 segment only. In accordance with the Midlerian terminology, therefore, I described the 

 fourth brachial of Eudiocrinus semperi as being or having a syzygy, after going into the 

 subject rather fully in two memoirs which were published in 1882. 6 Perrier, however, 

 in apparent ignorance of all that had been written on the subject by Muller, Dr. Carpenter, 

 and myself, not only introduces, though seemingly without knowing it, a new descriptive 

 terminology, but also imagines that I had used it before him. He has made a very 

 similar error in his description of Democrinus (Rhizocrinus) , and it is much to be desired 

 that for the sake of future workers he would take the trouble to acquaint himself with 

 the current nomenclature before writing his descriptions ; or at any rate that if he decides 

 to introduce a new descriptive method, he would make some statement to that effect. 

 The present result is that he describes a difference between Eudiocrinus atlanticus and 

 Eudiocrinus semperi or Eudiocrinus japonicus, which does not exist in reality. In all 

 three species alike there is a syzygy in the fourth brachial, as Midler would have described 

 it, with a pinnule on the epizygal. 



1 Joum. Linn. Soc. Lond. (Zool.), 1882, vol. xvi. p. 495. 2 Comptes renins, 1883, t. xevi. No. 11, p. 725. 



3 Abhamdl. d. k. Akad. d. Wiss. Berlin, 1849, p. 252. tProc. Zool. Soc. Lond., 1882, pp. 734, 735. 



5 Phil. Trans., 1866, p. 721. 



6 Joum. Linn. Soc. Lond. (Zool.), 1882, vol. xvi. p. 515 ; and Proc. Zool. Soc. Lond., 1882, pp. 734, 735. 



