A MONOGRAPH OF THE EXISTING CRINOIDS 435 



The cirri are XIV, 93-95, from 90 to 95 mm. long. The first segment is about 

 four times as broad as long, those following increasing in length so that the fourth is 

 twice as broad as long, the sixth is about as long as broad or slightly longer than broad, 

 and the tenth or thirteenth and three to five following are half again as long as broad. 

 The length then slowly decreases so that the segments in the terminal third of the 

 cirri are broader than long, becoming twice as broad as long on the last 25 or 30. 

 Distally when the segments have shortened so that they are about as long as broad 

 a terminal dorsal spine slowly develops which gradually comes to involve the entire 

 dorsal surface of the segments and becomes the typical dorsal spine characteristic of 

 this genus. The tip of the cirri tapers somewhat so that the terminal claw and the 

 penultimate segment are reduced and more or less rudimentary. The ends of the 

 basal rays are indicated by low, broad, inconspicuous swellings. The radials are 

 about four times as broad as long, oblong, in close lateral apposition, with a high 

 arid very narrow median keel which rises very abruptly; in profile view the crest of 

 this keel is seen to be convex. The IBn are about twice as long as the radials, about 

 three times as broad as long, oblong, with a high narrow median keel having in pro- 

 file a more or less convex crest. The IBr 2 (axillaries) are rhombic with the lateral 

 angles truncated, twice as broad as long. The lateral sides are as long as those of the 

 radials, or half as long as those of the IBrj. They bear a high narrow median keel 

 which curves to one side or the other and does not quite reach the distal border of the 

 ossicle. The IIBr series are 2, resembling the IBr series. The 12 arms are 95 mm. 

 long. The first two brachials have high thin median carinate processes resembling 

 those on the division series, and the following brachials have a similar but much 

 lower median carination which after the brachials become triangular rises into a 

 broad overlapping spine. 



A specimen with 13 arms 80 mm. long has the centrodorsal long, truncated 

 conical, twice as high as broad at the base, and the cirri IX, 104-108, 85-100 mm. 

 long. The other specimen with 13 arms has three IIBr 2 series, each on a different 

 postradial series. 



A specimen with 15 arms 80 mm. long has the cirri IX, 78-95, 80-95 mm. long. 

 Another with 14 arms 85 mm. long has the cirri XII, 89-90, 85 mm. long. A small 

 specimen with 10 arms 60 mm. long has the cirri 55 mm. long. 



Prof. F. Jeffrey Bell regarded all the specimens from the Sahul Bank (repre- 

 senting A. mirifica and A. anihus) as belonging to Carpenter's longicirra. He said: 



Dr. Carpenter founded this species on a single specimen and was therefore unacquainted with 

 the very considerable range of variation in the length of the cirri in different specimens of this 

 species. While one specimen may have cirri 80 or more millim. long, as in the type, in others the 

 cirri may not be more than 60 millim. long. In this point, therefore, the cirri may be more like 

 those of A. incerta than of A. longicirra. The present specimens are shown, by the simple condition 

 of the second pinnule and the comparative shortness of the joints of the cirri, to belong to A. longi- 

 cirra. When I first noticed the variation in the length of the cirri, I thought it might be possible 

 to show that the two species (A. incerta and A. longicirra) should be united. The other distinctive 

 characters, however, on which Carpenter insists seem, so far as A. longicirra is concerned, to be 

 constant, and with the present condition of our collections the species can still be readily distinguished. 



The description of the species as given is based upon the single specimen from the 

 Sahul Bank, the type, in the Indian Museum at Calcutta. In 1910 I examined three 

 additional specimens in the British Museum. One of these has the arms 105 mm. 



