26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 00 



PETASOMETRA HELIANTHOIDES, new species 



I. South Passage, Sharks Bay, 9 meters; Drs. Michaclsen and 

 Hartmeyer; June 16, 1905. — One fine specimen, which may be de- 

 scribed as follows : 



Centrodorsal thin discoidal, with a broad flat dorsal pole 4 mm. in 

 diameter ; cirrus sockets arranged in a single regular closely crowded 

 marginal row. 



Cirri XIX, 28-31, 20 mm. to 22 mm. long; the cirrus segments are 

 subequal, about twice as broad as long, the basal shorter, the last 

 five or six becoming somewhat longer ; the dorsal surface of the 

 segments is broad and flat; the second has the distal dorsal edge 

 produced and bluntly serrate ; on the following this serrate ridge 

 becomes more and more deeply crescentic, on the fourteenth and 

 following becoming a median straight finely, and rather bluntly, ser- 

 rate transverse ridge appearing as a minute spine in lateral view ; 

 opposing spine large, the apex subterminal, arising from the entire 

 dorsal surface of the penultimate segment, rising to a height about 

 equal to one-half of the diameter of the penultimate segment ; owing 

 to the closely crowded condition of the cirrus sockets the first three 

 segments of the cirri are sharply flattened laterally as in related 

 forms. 



The radials are concealed in the median line, but are visible as low 

 triangles in the angles of the calyx ; the IBr x are very short, about six 

 times as broad as long, the proximal and distal edges parallel to each 

 other, and the lateral edges parallel to the longitudinal axis of the 

 ossicle, not in lateral contact ; axillaries very broadly pentagonal, 

 from two to three times as broad as long, the lateral edges about two- 

 thirds as long as those of the I Br,, turned slightly outward and there- 

 fore making a slight angle with the longitudinal axis ; the lateral 

 corners of the IBr x and of the IBr axillary are rounded off ; there are 

 ten IIBr 4(3 + 4) series and two IIIBr 4(3 + 4) series, both of the 

 latter developed on the same IIBr series; the division series are 

 strongly rounded dorsally without lateral borders, resembling those 

 of Heterometra savignii. 



The twenty-two arms are 85 mm. long; the first two brachials are 

 subequal, slightly wedge-shaped, about four times as broad as the 

 median length ; the first is internally united for the proximal two- 

 thirds, beyond this point diverging at a right angle ; the first syzygial 

 pair (composed of the third and fourth brachials) oblong, two and 

 one-half times as broad as long; the next four brachials are short. 

 approximately oblong, about four times as broad as long, the follow- 



