A MONOGRAPH OF THE EXISTING CRINOIDS 



81 



is variable. In one of the large specimens it is found as a rule from between brachials 

 9 + 10 to between brachials 11 + 12. In the other large specimen it is sometimes be- 

 tween brachials 6 + 7 and sometimes between brachials 13+14, 14+15, or 16+17, 

 on one arm being between brachials 20 + 21. So far as may be judged from the few 

 arms preserved, the distal intersyx.jgial interval is 4-7 muscular articulations. 



Especially characteristic is P,, which is stiff and so stout as to influence the form 

 of the second brachial. The only PI preserved on the two large specimens is 8 mm. 

 long and is composed of 12 segments of which the first is short, the second is longer 

 than broad, the third, fourth, and fifth are strikingly long, and those succeeding are 

 again shorter, but still elongated. The second segment is much broader proximally 

 than distally. Sometimes the fourth segment is extraordinarily long, though this is 

 not at all the rule. P a is shorter and is composed of about 7 segments which with the 

 exception of the first are elongated and cylindrical. P 2 is of about the same length 

 as P] and is composed of about the same number of segments, but lacks the strong 

 broadening of the base. P b is of about the same size as P 2 . P 3 is sometimes markedly 

 shorter than P 2 , but sometimes of equal length; the first two segments are short and 

 the remainder are elongated. The average number of segments is 8. The length of 

 the segments decreases on this and the pinnules following. P 4 , which is general in 

 shorter than P 3 , is composed of two short basal segments which are followed by about 

 5 elongated segments. From P d the length of the pinnules and the number of their 

 component segments again increase. The number of segments reaches about 11, 

 of which ah 1 are shorter than those of PI. 



In the middle arm region there occur pinnules of which the segments, with the 

 exception of the distal, as a result of lateral broadening have a thickset appearance 

 and seem rather short. Later there are pinnules with about four short basal segments. 

 All the pinnules, but especially the proximal, have a stiff character. No statements 

 can be made in regard to the pinnules of the arm tips as these in the specimens at 

 hand are all broken. The sacculi on the pinnules are numerous, large, and dark 

 colored, as they are also on the arms. The dark color of the ambulacra! side of the 

 pinnules is due to the large number of sacculi. 



The preceding description is adapted from Hartlaub 's description of three much 

 broken specimens which were sent him with the Blake collection after the death of 

 Dr. P. H. Carpenter. They were without a label. One of the specimens was very 

 small. Hartlaub said that apparently one of the three specimens was Pourtales's 

 type specimen, though this is not certain. 



Hartlaub said that the relatively short and broad segments of the pinnules in the 

 middle arm region are naturally excavated for the reception of the ambulacra! soft 

 parts the genital cord, water vascular system, etc. so that these lie rather deeply. 

 They are only loosely attached and may easily be lifted out with a needle. 



The ambulacral soft parts are broadest at the third segment, where also the dark 

 color begins, and gradually decrease in width distally. The broad base is the result 

 of the expansion of the genital cord into a gonad. On uninjured pinnules it may be 

 seen that from the sides of the pinnule segments an exceedingly fine, fragile, and to all 

 appearances continuous layer of skeletal substance extends over the ambulacral groove. 

 In most of the cases observed by Hartlaub this fine calcareous investment was evi- 

 dently broken so that he was not able to determine whether as a rule the fine calcareous 





