216 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



In 1932 Dr. Hubert Lyman Clark recorded a single small specimen from Magneto 

 station XIV, in 19 fathoms, that had been collected during the work of the Great 

 Barrier Reef Expedition, 1928-1929. 



OUGOMETRA SERRIPINNA (P. H. Carpenter) 



Diagnostic features. Segments of P 2 mostly, or largely, longer than, or at least as 

 long as, broad, with the distal ends of the prismatic ridges more or less strongly 

 produced, or with one or more spines. 



Remarks. In addition to the typical form and the minor variations associated 

 with it, Oligometra serripinna has seven strongly marked varieties each more or less 

 definitely restricted to a limited region that deserve special notice. 



In the same region, if not actually at the same station, serripinna is found with 

 erinacea, imbricata, macrobrachius, and occidentalis. These forms may therefore be 

 regarded as localized varieties. Typical serripinna has not been found in the areas 

 inhabited by electrae, chinensis, or caledoniae. These forms may therefore be regarded 

 as true geographical races or subspecies. 



It has seemed most practicable to treat each of these forms separately. 



KEY TO THE VARIETIES AND SUBSPECIES OF OLIGOMETRA SERRIPINNA 



a 1 . Distal edges of the brachials in the proxtnial third of the arm turned abruptly outward and 



much produced. 



6'. Distal edges of the brachials in the proximal third of the arm turned abruptly outward and 

 greatly produced, with a scalloped and irregular crest; proximal to the second syzygy this 

 eversion becomes restricted to the central portion of the distal edge and may be more or less 

 resolved into high tubercles or blunt spines; anterior angle or axillary usually produced 

 dorsalward, or bearing three prominent tubercles; lateral processes of the segments of P 2 

 high and broad, usually with a truncated distal angle (northeastern Ceylon; 9-13 [or 11-15] 



meters) var. erinacea (p. 237) 



6 2 . No modification of the produced distal edges of the lower brachials, or of the edges of the 

 elements of the IBr series; segments of P 2 usually with very slight lateral processes (Ganjam 



coast, Madras Presidency, India; ?Tranquebar; 44-55 meters) var. imbricata (p. 236) 



a 2 . Production of the distal edges of the earlier brachials moderate or lacking. 



6 1 . Very ornate, with extravagantly developed processes on the proximal pinnules (Red Sea, 



off Eritrea; 36 meters) var. electrae (p. 241) 



6 2 . Not ornate; processes on the proximal pinnules not extravagantly developed. 



c 1 . Outer cirrus segments all with a transverse ridge, sometimes narrowed terminally into a 



median tubercle; P a present; arms not more than 83 mm. long, aud seldom over 60 mm. 

 d 1 . P 2 not greatly enlarged, becoming delicate distally, with the distal segments twice as long 

 as broad or even longer, the profile serrate in the distal half; cirri relatively long and 

 slender, with up to 24 segments; second-fourth segments of lower pinnules narrowly 



carinate (Province of Fukien, China; littoral) subsp. chinensis (p. 244) 



d 2 . P 2 stouter, markedly enlarged; cirri shorter and stouter with usually 18-20 segments; 



earlier segments of proximal pinnules not carinate. 



e 1 . Profile of P 2 strongly serrate (from Hong Kong, the Macclesfield Bank, and the Philip- 

 pine Islands southward to New Guinea and westward to the Pedro Shoal, the Mai- 

 dive Islands, and Bagamoyo, Tanganyika Territory; 0-91 [7183] meters). 



serripinna (p. 217) 

 e 2 . Profile of P 2 scarcely serrate. 



/'. Segments of the pinnules following P 2 with strongly projecting distal edges and 

 angles; P 2 with up to 19 segments (from Mauritius and Cargados Carajos to the 

 Red Sea; 0-55 meters) var. occidentalis (p. 239) 



