CALAMOCRINUS DIOMED.E. 27 



In Calamocrinus, as in other Neocrinoids except Hyocrinus, the pinnnles 

 are small compared with the arm of which they form a part. In Hyocrinus, 

 as noted by Carpenter, the pinnule-bearing joints have rather the appear- 

 ance of axillaries (Chall. Kep., Plate VI. Figs. 1-3), and resemble the axillary 

 of the end of an arm of P. decoru.s (Chall. Rep., Plate XXXV. Fig. 1). 

 The axillary which bears the last pinnule and the continuation of the arm 

 can scarcely be distinguished except by the greater length of the joints. 



Carpenter has called attention to the axillai-y appearance of the pinnule- 

 bearing joints in Rliizocrinus (Chall. Rep., Plate IX. Figs. 4, 5) and in Hyo- 

 crinus (Chall. Rep., Plate VI. Figs. 1, 2); and hence it is natural that an 

 axillary, " conceding the fundamental identity of the arms and pinnules," 

 should not give rise to arms and a pinnule also (Chall. Rep., p. 60). 



In Calamocrinus the joints next the radials are syzygial. In Rhizocrinus 

 lofotensis the first pinnule is on the eighth brachial, and in R. Rawsoni on 

 the sixth (Chall. Rep., p. 47). In Atelecrinus there are no pinnules until 

 the twelfth brachial. 



Bearing in mind the generally received identity of an arm and a pinnule, 

 it is difficult to understand the position taken by Walther.* According to 

 him, there are no less than five ^orimary embryonic pinnules (tentacles), 

 ten secondary, and ten tertiary ones, before the arms begin to form. Such 

 is also the case in the young Starfishes, young Echini, and young Ophi- 

 urans ; there are three pairs of tentacles and an odd one before we may 

 say that the ambulacral tube and its arms begin to form. But there is 

 nothing to show that the five primary pinnules (tentacles) develop into the 

 regular pinnules, and I cannot understand the figures of Walther in Plate 

 XXVI. Figs. 3% 3\ What is the first plate at the base of his pinnules 

 unless it be a radial ? He suggests that the pinnules are not branches of 

 the arms, but that the arms must be considei'ed as carriers of the pinnules; 

 that the early Crinoids had pinnules and no arms, and that the arms only 

 originated in the course of palasontological development ; and that we can 

 in no wise regard the pinnules as modified arms ; and he gives various other 

 physiological reasons which are in direct contradiction with the observa- 

 tions of the most careful investigators of Crinoids. If there is one pinnule 

 only on a joint, what becomes of the fossil genera in which there are two ? 

 He thinks he has discovered in the hook-like joint of the axillary the 



* Walther, Johannes, Untersuohungeii Uber den Bau der Crinoiden. Palseontog , XXXII., 1S86, 

 p. 155. 



