116 BULLETIN 75, UNITED STATES NATIONAL MUSEUM. 



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

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

 typical form and Jcennerlyi 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'. In addition to the usual small supplementary plates, adjacent to the upper arm 

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



mirabilis. 



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



the upjser arm plate. 



B'. 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'-. 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 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 phiothrix-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, .bakeri. 

 C~. 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^l2-2 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. 



