PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 235 



with very sloping sides and a relatively small dorsal pole, the diameter of which is 

 from one third to one half that of the centrodorsal; conspicuous perisomic interradials 

 are present. 



Remarks [by A.M.C.]. — In my opinion the above diagnosis does not afford any 

 reliable character by which .4. duebeni can be distinguished from ^1. bifida and more par- 

 ticularly from A. bifida moroccana. The degree of enlargement of the cirri distally 

 is variable in bifida (see table 6, p. 229) and in 10 specimens from the Azores which 

 I take to be bifida moroccana, the ratio of the diameter of the dorsal pole to that of 

 the base of the centrodorsal varies from 0.47 to 0.64:1, averaging 0.55. In two small 

 specimens from Algiers the dorsal pole is 0.64 and 0.45 of the total diameter. In 

 Carpenter's figm-e of duebeni the ratio appears to be about 0.5:1. With only three 

 specimens known from the western tropical Atlantic little idea can be obtained of the 

 range of variation. 



The preceding paragraph was wi'itten without knowledge of Gislen's Atlantide 

 report in which he reduced moroccana, together with hupjeri, to the synonymy of 

 A. duebeni. He may well be right about moroccana and duebeni but I believe much more 

 precise information is needed before the relationships between both of these and 

 A. bifida can properly be appreciated and that it is premature to synonjonize two of 

 theni without more reference to the third, especially when so little is known of the 

 West Atlantic form. 



Description.— The centrodorsal is pentagonal, 2.5 mm. broad and 1 mm. high, 

 the bare dorsal pole 1 mm. in diameter. 



The cirri are XXX-XL, 12-15; the segments in the middle of the cirri are broader 

 than long and somewhat compressed laterally. 



The disk is 7 mm. in diameter. 



A cluster of perisomic interradials lies between the ends of the IBr,. 



The radials are almost entirely concealed. The IBrj are verj' short, oblong, not 

 united laterally. The IBrj (axillaries) are acutely triangular. 



The 10 arms are about 45 mm. long. The first two brachials are appro.ximately 

 similar in shape, oblong or subtriangular, the second bemg rather the longer. A few 

 brachials after the second sj-z_vgy may be triangular, but they soon become wedge- 

 shaped with the articulations but Uttle inclined so as to be somewhat squarish in 

 outline, and distallj' elongated. The lower and middle brachials may overlap more 

 or less, but the distal parts of the arms are almost smooth. 



Syzygies occur between brachials 3+4, 9 + 10, 14 + 15, and distallj' at intervals 

 of from 2 to 7 muscular articulations. 



P, reaches over 10 mm. in length and is composed of 24 to 30 elongated and 

 overlapping segments. P2 and the following pinnules are about half as long with 

 12 to 14 segments which are much longer than broad. The distal pinnules are very 

 long and slender. 



According to Bohlsche the whole surface of the brachials and pinnule segments 

 is covered with fine longitudinal striations which end at the distal borders in fine 

 spinules. 



The color in alcohol is brown. 



Notes on a second specimen. — The cirri are about XXX, 12, about 7 mm. long. 

 In lateral view the outer cirrus segments are twice as broad as the proximal, strongly 

 flattened and with a straight dorsal profile. 



