116 BULLETIN 75, UNITED STATES NATIONAL MUSEUM. 



twenty-nine stations, where japonica also occurred, and at five of 

 these stations kennerlyi was also taken; at four other stations the 

 typical form and Icennerlyi occurred together. In view of these facts, 

 I retain the names therefore simply to designate certain well-marked 

 forms, which it is convenient to distinguish on account of their 

 striking difference in appearance. In order to make as clear as pos- 

 sible the conclusions to which I have been led regarding the members 

 of this genus, I give herewith an artificial key to the species and 

 varieties of Ophiopholis. 



KEY TO- SPECIES AND VARIETIES OF OPHIOPHOLIS. 



A 1 . In addition to the usual small supplementary plates, adjacent to the upper arm 

 plates, there is a large, distinct plate on each side of each upper arm plate. 



mirabilis. 

 A. 2 . No one of the supplementary upper arm plates differentiated as an accessory to 



the upper arm plate. 



B 1 . Supplementary upper arm plates confined to a transverse series, distal to 

 each arm plate, and not present at their sides; under arm plates short, 

 very much wider than long; arms short, only about 3-5 times disk diameter. 



brachyaclis. 



B 2 . Supplementary upper arm plates present, and often particularly abundant 

 at sides of upper arm plates; under arm plates usually almost or quite as 

 long as wide; arms usually more than five times disk diameter. 

 C 1 . Supplementary plates very small, often mere pointed granules, commonly 

 not in contact with each other along distal margin of upper arm plates; 

 latter more or less nearly circular, or longer than wide (sometimes wider 

 than long), usually more or less swollen distally; disk spines very slender 

 and acicular, or minutely thorny and with several points; general appear- 

 ance remarkably Ophiothrix-like. 



Radial shields large and bare; disk spines few and long; arm spines 



very long longispina. 



Radial shields and disk, more or less completely covered by very 

 slender, more or less thorny spines; arm spines moderately long. .baJceri. 

 C 2 . Supplementary plates very variable, often large and angular, often small 

 but angular, sometimes rounded and granule-like but usually in more or 

 less close contact distal to upper arm plates; latter more or less trans- 

 verse oval, sometimes circular, but usually much wider than long, little or 



not at all swollen distally; disk spines coarse or wanting aculeata. 



Supplementary plates small, numerous, often rounded particularly 

 at sides of upper arm plates; arm spines long and pointed=H-2 arm 

 joints; radial shields usually bare and conspicuous, longer than wide; 



disk with or without spines aculeata var. japonica. 



Supplementary plates more or less numerous (ten to twenty-four to 

 each upper arm plate), angular or rounded; arm spines=f-l arm joints, 

 blunt; radial shields covered, or if bare, nearly circular; disk with or 

 (more commonly in Atlantic specimens) without spines. 



aculeata var. typica. 



Supplementary plates few (six to ten to each upper arm plate), large, 

 angular and crowded; arm spines short, rarely equal to a joint; disk 

 without spines aculeata var. kennerlyi. 



