630 



BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



H 



VOLUME 1 



a 



FIGURE 35. Isometra johanni sp. nov. : a, Holotype, calyx less centrodorsal; b, B.M., 

 1948.1.7.196, B.A.N.Z.A.R.E. station 40, cirrus; c, holotype, part of arm with P, 

 to P 3 ; d, P. 



and are 3 mm. in length. The stem is incomplete, having 31 columnals. It is of the 

 bourgueticrinoid type. The second columnal is very short and is produced into a 

 lobe in each interradius. The third and fourth are narrower but equally short. The 

 fifth is about half as long as broad. The following columnals are elongated, about 

 three times as long as broad. Towards the end of what remains of the stem they 

 again become shorter. The smaller pentacrinoid is much younger. The broken stem 

 has 25 columnals. The first is short, with a depression in each radius, from four of 

 which the rudiments of the first cirri arise. The longest columnals are about twice as 

 long as broad. The sides of the basiradial cup are nearly straight. The basals and 

 the radials are of about the same length. The articulation of the IBr t occupies about 

 half the distal border of the radial. The orals are in contact with the radials and in 

 contact with one another by their lateral edges, so that they form a dome over the 

 disk. The radianal rests on the posterior oral near the IBr, of the right posterior ray. 

 The arms are of 13 to 14 brachials. They have strong side plates and sacculi are 

 present. There are no pinnules. The complete crown is about 4.5 mm. long. 



A young specimen also from station 107, has most of the arms broken at 5 to 6 

 mm. from the base but two are nearly 10 mm. long and were probably at least 12 mm. 

 long when complete. The single mature cirrus has 1 9 segments and is similar to those 

 of the adult. There is a complete, though narrow, circlet of basal plates. The radials 

 are massive ; each is produced on either side into a long interradial process which runs 

 up alongside the IBrj for the whole of its length. In the midline the distal edge of the 

 radial is everted into a prominent lip. The division series and lower brachials are 

 slightly carinate in the midline. Their lateral edges are straight. The only oral 

 pinnule developed is P u which is about 1.5 mm. long and has 6 segments, of which the 

 third to fifth are about four times as long as broad. The next pinnule is P 5 on the 

 twelfth brachial. It has 9 segments and is 3 mm. long. 



