The Crinoids from Dr, S. Bock's Expedition to Japan 19 14-. 133 



(18—20) pinnulars on P^ — P3, (P3 > P2 > PJ, and usually has somewhat 

 fewer cirrals. An examination of more ample material will probably 

 show that the two forms belong to tlie same species. 



A. H. Clark 1918 in the Siboga work gives Antcdon 'ininuia as 

 a synonymous form of /. adrestine. If tliis is correct iliere might 

 be a mistake in the description of the first-mentioned species. /. adresline 

 is said to have P^ 19; 10 mm. and in tiiis ease A. minuta can scarcely 

 have Pj 18; 3 mm. because of a rule that one always finds verified 

 in the examination of growth-series of Crinoids and that runs thus: 

 Length and number of segments of a cirrus, an arm or a pinnule 

 stand in a certain relation to the ontogenetical development and in a 

 certain relative proportion, viz. that younger specimens ha\e shorter 

 cirri, arms, and pinnules and fewer cirrals and pinnulars, than the full- 

 grown ones. The figures obtained by these characteristics are rather 

 constant in relation to one another at a given size and when compared 

 with the same characteristic in older and younger individuals of the 

 same species they can be fitted into an arithmetical series. 



Dorometra A. H. Clakk. 

 D. nana (Hartlaub). 



Fig. 123, 12-1. 

 Syn.: See 1918 A. H. Clark Siboga Exp. Vol. 42 B, p. 21.6. 

 From St. 41: 3 specimens. 



Sp. I (St. 41) The free, fiat, dorsal pole of Cd about 0,5 mm. C. 

 Li 10-14; 4—8 mm. P* segment short, 2^' cubical, 3"^ L = r/2 — 2 X 

 br, 4* — 7*'' segment: L = 2 — 3 X br, then shorter again. Antepenul- 

 timate cirral L = 1' 2 br, penultimate segment L = ICs br, with a pointed 

 opposing spine, h = '/2 of the br of the segment. Terminal claw cur- 

 ved, somewhat longer than the preceding segment. 



1 Br 1 almost concealed by Cd. Axillary rhombic, h = '■^/3 br 

 with a slight synarthrial tubercle in the proximal part. Arms X, 30 — 

 35 mm. Br — s 1 basally united inside. Br 2 with a small, backward 

 directed synarthrial tubercle; this ossicle is narrower than Br 1, by 

 which a broad interspace (= ^2 of the br of the arm) arises between 

 the arm-bases. Syzygies: 3 + 4, 9 + 10, 14 + !5 etc. with an interval 



