A MONOGRAPH OF THE EXISTING CRINOIDS 31 



Antedon spinifera var. brevispina Hartlaub, Mem. Mus. Comp. Zool., vol. 27, No. 4, April 1912, 

 p. 362, second line (characters; Montserrat, 88 fathoms [Blake station 155], and St. Lucia, 278 

 fathoms [Investigator] ), pi. 2, fig. 7 (St. Lucia, 278 fathoms). 



Description. — The centrodorsal is very small, hemispherical or low-conical, the 

 bare apical area convex and spinous. The cirrus sockets are arranged in 10 crowded 

 columns, one or two in each column. 



The cirri are XI-XX, 40-80, from 35 to 50 mm. long, or from one-third to half 

 the arm length. The longest cirrus segments, the sixth or seventh, are usually between 

 two and three times as long as broad and are centrally constricted; the distal cirrus 

 segments are very short. The segments beyond the basal third of the cirri are pro- 

 vided with long, slender, and sharp dorsal spines. 



The radials are over twice as broad as long with a prominent median spine. The 

 IBr, are short, between two and three times as broad as long. The IBr 2 (axillaries) 

 are almost triangular. The IIBr, IIIBr, and IVBr series are 2, similar to the IBr series 

 but with the component ossicles progressively longer. Slight synarthrial tubercles 

 are present. The elements of the division series are bordered with stout spines, with 

 occasionally other spines scattered over the dorsal surface. 



The 25-30 or more arms are from 65 to 140 mm. long. The lower brachials are 

 about as long as broad with parallel sides and very prominent articulations. After 

 about the eighth the brachials become wedge-shaped with concave anterior and pos- 

 terior borders, gradually becoming more elongate distally. The first eight or nine 

 brachials, like the elements of the division series, are bordered with stout spines, some- 

 times with other spines scattered over the dorsal surface. Beyond the eighth or ninth 

 brachial these spinous edgings become obsolete and strong, elongate, curved, and 

 overlapping processes develop on alternating sides of the median line. These processes 

 gradually approach the median line, at the same time becoming somewhat smaller, 

 until in the outer part of the arm they are relatively small, median in position, and 

 finally disappear altogether. This feature is subject to great variation; in some speci- 

 mens it is extraordinarily developed, in others almost entirely lacking. 



Syzygies occur between brachials 3 + 4, again from between brachials 26 + 27 to 

 between brachials 32 + 33, and distally at intervals of 4-9 musuclar articulations, the 

 lesser number being found in the more distal portion of the arms. 



In an average large specimen Pi is 7 mm. long with 15 segments of which the 

 first two are about as long as broad and the remainder become progressively elongated. 

 P 2 is 11 mm. long; the first segment is about as long as broad, the others elongated. 

 P 3 resembles P,. P« is similar, but shorter. These pinnules are all slender and stiff. 

 From P s to about F u the pinnules are slightly shorter than P 4 but stouter and strongly 

 carinate dorsally; the first segment is somewhat trapezoidal, the second is enlarged and 

 about as long as broad, and those following are smaller and somewhat longer than broad. 

 The distal pinnules are slightly longer and more slender with the enlargement of the 

 second segment not quite so strongly marked. 



The color "varies from almost white through pale straw color to a light yellowish 

 brown." Small specimens are the lightest and large specimens the darkest. 



Notes— The specimens from Albatross station 2354 are of average size. 



