359 
of Edinlurgh, Session 1883-84. 
“ Porcupine ” Crinoids. This, however, is not quite accurate, for 
there is no mention of any calyx-plates below the radials, the lower 
portion of the head being said to consist “ of a gradually expanding 
funnel-shaped piece, which, seems to be composed of coalesced upper 
stem-joints.” Subsequently, however. Sir Wyville found that in 
B. aldricliianus, from the Southern Sea, there is “ a series of basals 
which are soldered together into a small ring, scarcely to be distin- 
guished from the upper stem-joint.”* The existence of basals in 
Ilijcrinus {Bathycrinus) carpenteri was also recognised by Daniels- 
sen & Keren, f who were fortunately able to see the interbasal 
sutures in young individuals, though they entirely disappear in the 
adult j and there is a similar basal ring in B. gracilis, intervening 
between the radials and the numerous thin joints at the top of the 
stem. 
The two outer radials and the two lowest brachials of B. gracilis, 
and also of B. aldrichianus, were described by Sir Wyville as re- 
spectively united by syzygy, while Danielssen and Koren made the 
same statement respecting B. carpenteri. In all these cases, how- 
ever, the supposed syzygy is really a modification of the ordinary 
bifascial articulation permitting lateral movement only, which is so 
common in the Gomahdm, and is also characteristic of four species 
of Pentacrinus ; for a third and smaller bundle of fibres is inserted 
into a deep pit at the lower or dorsal end of the vertical articular 
ridge on each joint-face. Externally, this form of articulation looks 
very much like a syzygy, as the joints are brought into closer con- 
nection than when they are united by a pair of muscular bundles. 
But a glance at their terminal faces is sufficient to show that the 
plainness of Pentacrinus or Rhizocrinus, or the striation of the 
Comatula-^jzjfiQS, is altogether absent, and that they are marked 
by distinct ridges and fossae. 
According to Sir Wyville’s description, there are none of these 
so-called “ syzygies ” in the arms of B. gracilis beyond that between 
the first two joints ; while in B. aldrichianus there is a syzygy 
between the fourth and fifth brachials, and at irregular intervals 
beyond them ; but the “ alternate syzygies in the arms, which form 
* “Notice of new living Crinoids belonging to the Apiocrinidee,” Journ. 
Linn. Soc. Zool., vol. xiii. p. 50. 
\ Nyt. Mag. for Naturvidskaherne, Bind. 23, p. 4. 
