A MONOGRAPH OF THE EXISTING CRINOIDS 295 



In the same specimen P on another arm is abnormally short 3 mm. long with only 11 

 segments shorter than P 3 of the same arm, which is 5 mm. long with 16 segments. The 

 form of the broader proximal segments of P a and Pj varies, even hi the same specimen. 

 Sometimes the second-sixth segments are more triangular, sometimes more quadrangu- 

 lar. On some P 2 the third and fourth, or in addition the second and third, segments 

 of one side have an especially long keel, a feature which in other pinnules of the same 

 type is not evident. P b and P 3 are generally somewhat shorter, 5-6 mm. long with 

 14-16 segments, and about 6 broad proximal segments of which the second-fourth or 

 second-sixth are singly or doubly carinate, and the 8-10 outer are elongate and small; 

 the crest of the keels may be either smooth or dentate. The pinnules following P e , 

 P 4 , and P a are on the average shorter, about 4-5 mm. long with 10-13 segments; in 

 the form of the basal segments, in the number of their segments, and in their length, 

 they form a transition to the pinnules of the brachials succeeding and the middle of the 

 arm, up to about the fifteenth brachial. These pinnules are short; almost always two 

 thick and broad basal segments may be recognized, followed by 7-10 elongated ones. 

 This type of pinnule can be shown to be typical for the middle of the arm hi all the speci- 

 mens. Preponderating by far are pinnules 3 mm., seldom 4 mm., long with 9 segments; 

 variants are pinnules with three broad basal segments, and others 5 mm. long with 1 1-12 

 segments. Toward the arm tips there appears to be no increase in the length of the 

 pinnules, but because of the poor state of preservation of the arm tips Hartlaub was 

 unable to make a definite statement in regard to this. 



The ambulacral plating of the pinnules consists of well developed side- and covering- 

 plates. The sacculi are rather small and inconspicuous. The disk is deeply incised, 

 8-10 mm. in diameter, brown in color. 



In alcohol the centrodorsal and post-radial series as far as the third brachial are 

 dark -brownish to brown -with the remaining brachials and the cirri white. 



Localities. -Blake stations 34, 157, 158, also St. Vincent; Albatross stations 2161, 

 2752, 2753; Atlantis stations 2950, 2980, 2980A, 2980B, 2982A, 2982B, 2982C, 2983, 

 2983A, 2984, 2987, 2999, 3000, 3303, 3326, 3372, 3388, 3425, 3430, 3431, 3432, 3434, 

 3435, 3436, 3438, 3466, 3467, 3478, 3482 ; off St. Croix. For the details of these stations 

 see page 339. 



Geographical range. From the Yucatan Bank, Cuba, and the southern Bahamas 

 southward along the Antillean chain to St. Vincent. 



Bathymetrical range. From 267 to 548 meters. 



Thermal range. One record, 8.89 C. 



Remarks. Dr. H. L. Clark recorded 272 specimens of this form from the Atlantis 

 stations given. It seems unlikely that all of these really belong to it; some of the other 

 related forms surely should be represented in such extensive material. A detailed 

 study of the Atlantis specimens is much to be desired. 



Dr. Clark said that several of the specimens were still attached to the sponges 

 upon which they apparently often live. Most of them still retained some trace of a 

 bright yellow color which is very marked in many specimens and was apparently the 

 normal color in life; in large specimens the calyx and base of the arms is darker and 

 duller, an indistinctive gray-brown. Dry material is often more or less bleached, 

 sometimes nearly white. The size of the specimens ranged from about 8-10 mm. 

 across the disk, with arms 50 mm. long, more or less, to big adults 20-25 mm. across 



