I'i 111 I.I.I ■'.TIN 76, I MTED STATES NATIONAL MUSEUM 



not uncommon to find these narrow areas all along the side of the abactinal area, 

 and some of them extend without interruption from the carina] to the supermarginal 

 plates. They are accentuated by drying. The abactinal spinelets sire small (0.4 

 to 0.7 mm. long) of variable caliber, but generally slender, distinctly clavate to 

 subcylindrical on the one hand or subcapitate on the other. They arc rather num- 

 erous and on accounl of the structure of the skeleton form many transverse lines. 

 and on the trabeeulae in lines either singly or in linear groups of two or three, 

 in thickness toward the carinals. The latter an- generally the largest, 



apitate or capitate, striate, and form a definable irregular longiseries. In most 

 specimens there is a supramarginal channel, immediately above which the spinelets 

 form a fairly well defined longitudinal dorsolateral series which is more prominent 

 in forma groenlandica. Even in forma crihraria there is considerable variation in 

 the caliber, shape, and uumber of the abactinal spinelets. In alcoholic specimens 

 the spin. 'lets appear to stand in transversely oriented groups, surrounded by deep 

 narrow creases in the pulpy integument. 



Superomarginal spines in a transverse -erics of two, three, or four, the median 

 (or second from the top generally the largest. They vary from slender to stout, 

 and from terete, slightly tapering to cylindrical or clavate, depending upon the 

 robustness of the general armature. On the same specimen the spines increase in 

 thickness and become much shorter toward the end of the ray, and they are stibequal 

 to or slightly larger than the abactinal spines. The series of combs is generally 

 'in:.' regular. Below them is a well-defined, and in some specimens rather broad, 

 intermarginal channel (showing huge papular areas when dried). There is great 

 variation tine in part to the shrinkage of the specimen in alcohol and in part to the 

 size of the gonads. Below this are two series of inferomarginal spines and one of 

 actinal. The latter extends a third or half the length of ray. These three series, 

 or two distally, have spines similar in form to the superomarginals but are a little 

 stouter and longer. In some examples the first half dozen inferomarginal plates are 

 monacanthid. The terminal plate (quaintly termed the "eyelid'' by Stimpson) is 



ly covered with stout clavate or subcapitate spinelets stouter than any others 

 immediately adjacent. 



Adambulacral plate typically diplacanthid, except distally where they are alter- 

 nately diplacanthid and monacanthid, or are mostly monacanthid. The spines are 

 slender terete, with bluntly rounded tips. The inner or marginal is likely to be 

 gentlj tapered, and slenderer than the outer, which is more often slightly "clavate. 

 The robustness of both varies with that of the general spinulation and is subject to 

 considerable variation. There are two plates in contact on the interradial line ex- 

 ternal to the oral plates. The first if conspicuously larger than the second. About 

 23 or 24 plates correspond to the first in inferomarginals. 



Tl '■' 1 l' la ' 1 '- »"''' typical of Leptasterias, with' one apical and one suboral spine 



''.' each l ,lll! ''. the former about us long as the median suture, but neither especially 

 diagnostic. The apical -pine is usually tapered. Verrill (1914, p. 149, fig. 7a) figures 

 the mouth plates with two apical spines each, one behind the other/ This is an 

 •"list - mistake, us 1 have been unable to find such an arrangement in any of my 

 specimens, including four from the same locality at which Yen-ill's example was 



