KEPOET ON THE CRINOTDEA. 285 



This would give the maximum number of arms as forty ; but although the ten distichal 

 axillaries may all be present, the palmar axillaries are frequently only developed on the 

 two outermost of every set of four secondary arms, as in the unique specimen of Penta- 

 G7-inus maclearanus (PI. XVI.), and the individual of Pentacvinus alternicirrus shown in 

 PI. XXV. This would give six arms on each ray, making thirty in all. Sometimes, 

 however, there are no palmars at all, or only one or two series of them (PI. XVIII. fig. 2 ; 

 PI. XIX. figs. 1, 6, 7), so that the number of arms varies between twenty and thirty. 



The ray-divisions of Pentacrinus decorus present almost as much variation as the 

 basals do. Some young specimens have only one or two distichal series (PI. XXXV.); 

 while one individual has but ten arms like Pentacrinmi naresianus. In others, again, the 

 arms are more numerous, though palmars are rare (PI. XXXVI. fig. l). I am inclined 

 to suspect, from an examination of several young specimens, that the many-armed 

 condition is to some extent a secondary one. Thus if none of the arms were broken 

 and subsequently repaired, the original of PL XXXV. fig. 1 would have grown up with 

 no more tlian eleven arms. When, however, an arm is broken oft" at a syzygy, and a new 

 one developed in its place, an axillary is nearly always formed in this new one sooner 

 or later, whether there were ojie present on the original arm or not. An instance of 

 this kind is shown in PL XXXVI. fig. 2; and it is not uncommon to meet with indi- 

 viduals of ten-armed species of Comatula which have replaced some of their arms after 

 fracture and have developed axillaries in the reparation, so that tlie number of arms may 

 reach eleven or twelve. This increase in the number of arms after reparation seems to take 

 place largely in Pentacrimis decorus ; for it is rare to meet with a specimen which does 

 not show these signs of reparation, certain axillaries and the arms which they bear being 

 distinctly smaller than their fellows. 



In Pentacrinus asterius and Pentacrinus milUeri there are always twenty arms or 

 more, all the primary arms ending in distichal axillaries. Most of the secondary arms bear 

 palmar axillaries, and there are sometimes even one or two more beyond these, so that 

 the rays may divide five times in all. There is no special regularity of division in 

 Pentacrinus asterius, though the number of arms is large, exceeding one hundred, 

 according to Sir Wyville Thomson.' But in Pentacrinus miilleri there are usually not 

 more than four raj'-divisions, the (palmar) axillaries being limited to the outer arms as in 

 Pentacrinus maclearanus and Pentacrinus alter nicir rus ; while the fourth and fifth 

 axillaries, if present, occupy a similar position, so that there are six, eight, or ten arms to 

 the ray, as 2,1; 1,2—2,1,1; 1,1,2— or 2,1,1,1; 1,1,1,2. 



The arms oi. Metacrinus branch as a rule more freely than those oi Pentacrinus, except 

 Pentacrinus asterius, all of the species having two, and most of them four axillaries 

 l)eyond the radials ; but there is no special regularity about the grou^jing of the arm- 

 divisions, 



' Sea Lilies, Tlie Intellectual Observer, August 18G4, p. 5. 



