160 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



less oblique, and in the terminal portion much elongated and centrally constrict- 

 ed, twice as long as broad or even longer; fifth and following brachials with rather 

 strongly overlapping spinous distal edges, this feature becoming less marked in the 

 outer portion of the arm. 



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

 of 3 muscular articulations. 



PI is 11 mm. long, slender and flagellate, with from 30 to 32 segments, of which 

 the first is short, the following three or four about as long as broad, then rapidly be- 

 coming elongated and after three or four more about twice as long as broad, and 

 somewhat longer distally; second and two or three following segments with the distal 

 edges strongly produced, overlapping and finely spinous, but this gradually dies away 

 as the segments become elongated, so that most of the pinnule is smooth; the elon- 

 gated segments have slightly expanded ends. P 2 is 5 mm. long, slightly less stout 

 basally than P 1; with from 16 to 20 segments, of which the first is exceedingly short, 

 the next two are about as long as broad, and the following become elongated and 

 about twice as long as broad distally; second, third, and fourth segments with strongly 

 overlapping distal dorsal ends, this feature dying away on the tliree or four following 

 segments. P 3 is about 5 mm. long with about 15 segments, of which the proximal 

 have much more strongly produced and overlapping distal ends than those of Pj, 

 which it otherwise resembles, and this character is prominent on all the segments 

 almost to the tip of the pinnule; the third to twelfth segments bear a large rounded 

 gonad. The following pinnules are similar to P 3 but slightly longer, 5.5 mm., with 

 somewhat larger genital glands; after P IO the gonads slowly decrease in size, finally 

 disappearing on P 16 . The distal pinnules are exceedingly slender, about 4 mm. long, 

 their perisome with large, conspicuous and thickly set sacculi. 



Each of the ambulacral lappets contains a minute short straight rod. 



The disc is as in Antedon loveni; the sacculi are rather small, but very numerous 

 along the ambulacra of the disc, arms and pinnules. 



The color in alcohol is a dull greenish gray. 



[NOTES BY A.M.C.] It can be seen from the foregoing descriptions and table 

 that the types of lacertosa are very similar to those of incommoda. The most im- 

 portant difference seems to lie in the proportions of the cirri and number of segments, 

 the larger specimens of lacertosa with arm length about 65 mm. having cirri not more 

 than 7 mm. long, with up to 12 segments, while Port Phillip specimens with arm 

 length about 50 mm. have the cirri 8 mm. long, with 14 segments. The larger 

 number of segments in PI of lacertosa (30 to 32) is not so much greater than the 24 found 

 in one of the largest Port Phillip specimens, especially considering the very wide 

 range with regard to this character shown by Gisldn to occur in Antedon serrata which 

 has from 12 to 28 segments in PI in different specimens. 



Also included in the preceding table are details of three of the 11 specimens of 

 Antedon from Lewis Island in the Dampier Archipelago, just east of the northwest cape 

 of Australia. In retrospect Mr. A. H. Clark included these in A. iris in this typescript 

 but the cirrus segments are relatively much shorter than in the type of that species and 

 they approach the types of incommoda much more closely. The only significant dif- 

 ference appears to be that the centrodorsal of the Dampier Archipelago specimens is 

 less markedly discoidal than in the Port Phillip specimens, with the cirrus sockets en- 

 croaching further onto the dorsal pole, so that its diameter is not more than 0.9 mm. 

 and may be as little as 0.4 mm., though averaging 0.7 in the 11 specimens. This dif- 



