438 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



than broad, the longest, the fifth or sixth, being about half again as long as broad, and 

 those following are broader than long. The longer proximal cirrus segments are 

 slightly constricted centrally. The distal portion of the cirri is laterally compressed, 

 and the distal segments bear a low dorsal median keel. There are no dorsal processes. 

 The opposing spine is well developed. 



The radials and division series resemble those of S. i. protectus (page 443) ; the 

 IIIBr series are normally externally developed, but in one specimen examined they 

 are internal. The ossicles of the division series and first two brachials have more or 

 less developed ventrolateral processes. 



The 18-30 arms are 65-153 mm. long. The smooth and short brachials are at 

 first practically oblong, then becoming obliquely wedge-shaped, almost triangular, and 

 after about the thirtieth oblong again, and terminally longer than broad. 



Syzygies occur between brachials 3+4, from between brachials 14+15 to between 

 brachials 18+19, and distally at intervals of 6-11 muscular articulations. Sometimes 

 there is an additional syzygy between brachials 9+10. 



PI is about 6 mm. long, with about 20 segments, and resembles P! in S. i. protectus. 

 P a is much smaller than P,, with about 11 segments. P 2 is long, stiff, and spinelike, 

 becoming slender distally, 7-17 mm. long, with 16-20 segments. The first two seg- 

 ments are short and those following are elongate, those in the middle of the pinnule 

 being the longest. P 3 is small and weak, the smallest pinnule, with about 10 segments. 

 The pinnules following gradually increase in length, those in the middle of the arm 

 being 6-7 mm. long, with about 20 segments. 



Notes. The material from Mabahiss station 10 consists of arm fragments and a 

 detached disk representing two individuals. 



The specimen from motorboat station Id has 20 arms; the cirri have 17 or 18 

 segments; P 2 is 7 mm. long with 14-16 segments and becomes slender and delicate 

 terminally ; on one arm P 3 resembles P 2 . 



Two small and imperfect specimens from Suez Bay were referred to marginata 

 by Chadwick with some little doubt. He said that as in the type specimen the centro- 

 dorsal is a saucer-shaped disk marked with cirrus sockets almost to the center of the 

 dorsal surface and bears the cirri in an irregular row around its margin. The cirri 

 are XVII, 15-17 or even 19, the segments gradually increasing in length from the 

 first to the seventh, beyond which they are scarcely longer than broad and become 

 increasingly compressed, and are slightly carinate dorsally or even bear a minute 

 dorsal spine. The radials are distinctly visible and are not in contact except at their 

 proximal ends. In the type of marginata they are only just visible, but this point 

 of difference, Chadwick said, is possibly due to the immature condition of the Suez 

 specimens. The IBr series agree with those of the type. In one of the specimens 

 only IBr series are present. In the other there are two IIBr ossicles on one branch 

 of each postradial series, and in the case of one postradial series two IIIBr ossicles. 

 Syzygies occur between brachials 3+4, 9+10, and 16+17, and distally at intervals 

 of five or six muscular articulations. The proximal pinnules have fewer segments 

 than those of the type of marginata. PI has 14 segments, and P 2 has 14 or 15. P b is 

 little larger than P,, but has 15 or 16 segments, while P c has 11 or 12 segments and is 

 much smaller than P t . 



The specimen from the Seychelles is small. 



