HO BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



Forma ASPERA, new forma 



Plate 44, Figures 4, 4a-4c; Plate 45, Figures 2, 2a; Plate 51, Figure 4; Plate 52, Figure 6 



Diagnosis. — Differing from forma regularis with which it freely intergrades in 

 having relatively few dorsolateral spinelets; usually a definite adradial and supra- 

 marginal band free of spinelets; typically a single series of superomarginal, infero- 

 marginal and actinal spinelets; adambulacrals monacanthid; rays six, robust, typi- 

 cally with a thick skin; papulae large. It 43 mm., r 13 mm., br. 13 mm., R = 3.3 r 



(St. Paul, Kodiak). 



In this paucispinous, but robust phase of hexactis there are extreme specimens 

 with a'singlc prominent carinal series of usually contiguous subcylindrical truncate or 

 subcapitate spinelets; a single zigzag series of widely spaced dorsolaterals with a few 

 scattered spinelets at base of ray; superomarginals in one regular series, inferomar- 

 ginals in one or two; actinals in one series; meshes of abactinal skeleton rather open. 

 Then there are others in which accessory smaller carinal spinelets are added on some 

 of the lateral lobes of the plates, usually on the proximal part of ray only. (This 

 phase of spininess corresponds to that of Pisaster breiispinus forma paucispinus.) 



These specimens when dried have a rather rough, meager appearance in spite of 

 the stoutness of the rays. Owing to the thornlets of the spines the surface is raspy. 



Typical specimens are found at Nagai, Shumagin Islands; Kukak Bay, Shelikof 

 Strait; St. Paul, Kodiak; Litnik Bay, Afognak Island; Prince William Sound (Cor- 

 dova); Port Etches, Alaska; Funter Bay, Lynn Canal; Wrangell; WhiteWater Bay, 

 Alaska; and Alert Bay, Vancouver Island. 



Well developed types from St. Paul, Kodiak Island, have a regular prominent 

 series of close-set, subcapitate, striate, unequal, carinal tubercles. The dorsolateral 

 area is very irregularly beset with relatively few, widely spaced, unequal tubercles 

 becoming sometimes transverse groups of three or four. These increase in number 

 by interpolations until a broken areolated pattern of regularis is achieved. Some of 

 the dorsolateral tubercles are conspicuously heavier than the carinals or they are 

 subequal. There is usually a well-defined bare zone above the regular single series 

 of subcylindrical or tapered superomarginals. The latter define the dorsolateral 

 margin of ray. Frequently there is a similar adradial channel. Intermarginal 

 channel well marked. Inferomarginal spinelets usually one, sometimes two, tapered, 

 blunt, a little longer and heavier than upper series; actinals similar to above extending 

 in a single series far along ray. Adambulacral spinelets subclavate, about as long as 

 actinals, but much slenderer, gradually lengthening on first 6 to 10 plates; beyond 

 base of ray the alternates are slenderer and more advanced into furrow; mouth plates 

 with fairly well developed actinostomial spine, about as long as plate; occasionally 

 a second small companion; suboral longer than first adambulacral and actinostomial. 



The specimens from Kukak Bay, Shelikof Strait, Alaska, are notable for having 

 unusually slender ossicles and large papular areas. The spinelets are weaker than 

 normal and straight pedicellariae small. 



Specimens from the vicinity of Cordova, Prince William Sound, exhibit an 

 uninterrupted series from typical aspera to paucispinous examples of regidaris. 

 Some specimens of both forms have well developed ovoid straight pedicellariae on 

 the abactinal, lateral, and actinal surfaces. The skeletal meshes are large. 



