298 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



same width until near the end, the terminal portion again tapering slightly. The 

 first segment is very short and those following very gradually increase in length 

 to the eighth, which, with those succeeding, is about twice as broad as long. The 

 penultimate segment is about as long as broad. After the seventh or eighth 

 segment the dorsal profile of the segments becomes very strongly, though evenly, 

 convex, so that in a lateral view the dorsal profile of a cirrus as a whole is strongly 

 scalloped. The opposing spine is small, blunt, and inconspicuous. The terminal 

 claw is small and blunt. 



The radials are concealed by the centrodorsal. The IBri are very short, oblong, 

 almost or quite united laterally. They are united to the IBr 2 (auxiliaries) by syzygy, 

 the 2 ossicles together forming a pentagonal element which is about twice as broad 

 as long. The IBr 2 are free laterally. 



The 10 arms are apparently 60 or 65 mm. long. They are exceedingly stout 

 in the basal half, the brachials measuring between 3 and 4 mm. in width. The 

 dorsal surface of the arms is peculiarly flattened. The first brachial is exceedingly 

 short, forming what appears superficially to be a syzygial pair with the second, this 

 pair being wedge-shaped, about twice as broad as the median length, and interiorly 

 united with its neighbor. The third and fourth brachials form a syzygial pair which 

 is wedge-shaped and about twice as broad as the inner (greater) length. The fol- 

 lowing brachials are slightly wedge-shaped, about three times as broad as the median 

 length, gradually becoming triangular, from two and one-half to three times as broad 

 as the longer side. The whole arm presents an exceptionally rugged appearance. 



P! is 13 mm. long and is composed of 30 segments, of which the first 3 or 4 are 

 broader than long and the remainder are about as long as broad. None of the 

 segments are carinate. The terminal comb has 11 teeth which are bluntly trian- 

 gular, rather narrow basally, and about as high as the width of the segments bearing 

 them. P 2 is similar but not so long, as stout basally as P u but, owing to the lesser 

 length, tapering slightly more rapidly. P 3 is similar, 8.5 mm. long with 21 segments, 

 almost all of which are broader than long, as stout basally as P 2 but becoming more 

 slender distally. This pinnule bears no comb. The following pinnules are ap- 

 parently similar to P 3 , gradually becoming more slender distally with longer seg- 

 ments, the change taking place first in the distal portion of the pinnules and working 

 toward the base, and slightly decreasing in length. The segments in the proximal 

 part of the pinnules following P 3 are more or less produced in a thickened convexity 

 dorsally, this feature dying away in the outer half of the pinnule and slowly dis- 

 appearing from the pinnules in the distal half of the arm. 



The preceding description is based upon the 2 fragmentary specimens which 

 were originally described by Johannes Miiller under the name of Alecto rosea in 1841. 



In a specimen probably from the vicinity of Perth, Western Australia, all the 

 arms possess ambulacral grooves, but in the proximal portion of some of the arms 

 single pinnules, or groups of 2 or sometimes of 3, occur without grooves; in the outer 

 part of the arms occasional pinnules are found to be grooveless. There appears to be 

 no regularity in the occurrence of the grooveless pinnules, though the conditions can 

 not be worked out with certainty because of the poor state of preservation of the 

 specimen. The grooveless pinnules (vol. 1, pt. 2, pi. 50, fig. 1332) are at once 



