The Ceixoids from Dr. S. liocic's Kxi'EmTiox to Japan 1'.M4. 17.'» 



7 (1 + 2, 4 + 5) 4 cases: 12 mm. II Br— s 7 (3 + 4) 3 cases. (3 + 4) 

 2 cases, 1 1 (3 + 4 : 2; 2 + 2 : I) 3 cases; Jl— 13 mm. Ill Br~s <) 

 (3 + 4) 1 case, 11 (3 H- 4) 3 cases, 12: 1 case. 13 (3 1-4) 5 eases, 15 

 (3 + 4) 3 cases, 17 (3 + 4) 1 case, 1!) (3 14) 2 eases: <» — 17 mm. 

 IV Br— s 15 (3-14) 4 cases, 10 (4 + 5, 10-1- 11) 1 ease, 17 (3 + 4) 2 

 eases. 1!) (3 + 4) 1 ease, 21 (3 + 4) 1 case, 23 (3 + 4) 1 ease, 25 

 (3 + 4) I case, 27 (3 + 4) 1 case; 14—24 mm. V Br-s 15: I, 17: 1, 

 19: 2 eases (syzygy between 3 + 4); 15— 10 mm. Arms partly broken, 

 in a complete specimen probably about LX; total L 105 mm. Un- 

 branched arms 00 mm.: 10 — 20 mm. with rudimentary p — s. The 

 number of the segments of the |) s at tiie Iraiisition II, 11. 9. S. 7, 

 4, 3, 2, 2. Syzygies with an interval of about 20 oblique articulations. 



Pi (to the right on 1 Br 2 in 3 eases) 10 — 17; 12 nmi., 1\, 15; 

 9 mm., Pj,, 14; 8 mm. 



Disk 13 mm. Anal cone 4,.-. mm. 



The present material of M. interreptuH forms an extraoi'dinarily 

 fine and interesting series. Hp. 16 may be the youngest known stage 

 of recent pentacrinoids' or at least of the genus M.etacrimts. 



As to the thickness-growth of the stem one can observe that 

 the increase is most rapid among the young specimens and generally 

 decreases with growing age. When the diametei' of the stem is less than 

 1 mm. the stem thickens with 0,i mm. for a length-growth of about 

 15 nun. From l,o — 2,.^ nun. generally the same enlargement of the dia- 

 meter of the stem is reached with an length-growth of 25 nun. (.\n 

 exception is, however, Sp. 13, but one must notice that the pi-eserved 

 part of the stem is relatively short and the whole thickness-growth 

 only 0,1 mm.; the divergence might therefore be ascribed to errors of 

 measurement.) From 2,5 — 3,o mm. the diameter of the stem increases 

 with 0,1 mm. on 30 — 35 mm. Between 3,o and 4,o mm. the same growth 

 takes place on 00 — 120 mm. and over 4,o mm. an equivalent thick- 

 ening is attained on a length-growth of about SO mm. Fxceptions are 

 Sji. 11 with a thick stem, but rapid growth (0,i mm. pro 33 mm.) and 

 Si). 21, where the diameter of the stem is proximally decreasing. A 



' A figure of a very young specimen of hocrinus (/ecoruK of about the same size 

 is also presented by A H. Clark in 1908 (Proc. U. S. Nat. Mus. Vol. 35, p. 88; a stem frag- 

 ment) and in 1915 (Monograph p. 205; the same stem, here the figure is correctly placed) 

 and by H. L. Clark in 191 S (Bull. Lab. Nat. Hist. Iowa Vol. 7, Rep. Criii .»^- Echin. of the 

 Bahama Exp.). 



