PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 521 



III large specimens the ends of the basal rays are visible in the angles of the calyx 

 as small tubercles which only with difficulty are distinguishable from the general 

 surface of the centrodorsal and radials. They are not discernible in small individuals. 

 There are no subradial clefts. 



The distal edge of the radials is even with the rim of the centrodorsal in the median 

 lino (projecting for a slight distance beyond it in young individuals), but the radials 

 are produced upward in the angles of the calyx, where the truncated tip of the process 

 formed by two adjacent radials entirely separates the bases of the IBr,. The IBri are 

 relatively large, about two and a half times as broad as long, with the lateral l)orders 

 almost or quite straight and slightly convergent and the distal border straight or 

 slightly depressed in the center. The IBro (axillaries) are broadly pentagonal, from 

 about as long as broad to nearly half again as broad as long, with the lateral borders 

 not quite so long as those of the IBri with which they form a broadly obtuse angle, 

 and the lateral angles produced. The distal sides, which are only slightly concave, 

 form approximately a right angle with each other. 



The 10 arms are broken in all the known specimens, and usually lost at the first 

 syzyg3'. In the largest individuals the distance from the distal edge of the radials to 

 the first syzygy is 8.0 mm. The first brachials are shghtly wedge-shaped, about twice 

 as broad as the exterior (greater) length and entirely free interiorh*, their inner edges 

 making with each other an angle of about 90°. The second brachials are considerably 

 larger, not quite so long as broad. There is little or no trace of synarthrial tubercles. 



In a specimen from Siboga station 45 with the centrodorsal 4.0 to 4.5 mm. in 

 diameter. Pi is 10 mm. long with 22 segments, of which the first is short and the following 

 gradually increase in length, becoming about as long as broad on the eighth and two 

 or three times as long as broad terminally. The short earlier segments have their 

 corners cut away as in Heliometra. The pinnule is slender and becomes flagellate distally. 

 P2 is 10 mm. long \\^th 23 segments, resembling P,. P3 is 9 mm. long with 21 segments, 

 similar to but slightly more slender than the first two pinnules, very slight]}' less stout 

 basally, but tapering less rapidly and vvithout the flagellate tip. P4 is 8 mm. long with 

 18 segments, and resembles P3. Pi has the corners of the basal segments cut away 

 more than does P2, which itself has this feature more marked than does P3. Pi has a 

 longer flagellate tip than Po and is in general more flexible, and Pj difTers from P3 in 

 the same way. 



Notes. — In the type specimen of Ps. mira the sharply conical centrodorsal is 4 nmi. 

 broad at the base and 4 mm. high. The interradial furrows are shallow with a rounded 

 bottom, and the median column of cirrus sockets is represented bj' only a single socket 

 situated between the distal ends of the peripheral sockets in the two outer columns, 

 which columns come into contact just beyond it. 



In another specimen recorded in 1918 as Ps. mira the centrodorsal is relatively 

 longer, 4.0 mm. in diameter at the base and 4.25 mm. from the apex to the interradial 

 border. [Note by A.M.C: I have also measured this specimen and estimate the 

 basal diameter to be 4.5 mm. and the vertical height 3.9 mm.] 



In the type specimen of Ps.parva the centrodorsal is 3.2 mm. broad at the base and 

 4.0 mm. high. [Note by A.M.C: The vertical height is probably about 3.7 mm.] 

 There are no sockets between the lateral converging columns, but sometimes one of the 

 proximal sockets in these columns may be displaced more or less inwardly. The inter- 

 radial furrows are very shallow. An example from Investigator station IIG is similar. 



