272 BULLKTIN 76, UNITED STATES NATIONAL MUSEUM. 



for example H. aspera, II. leviuscula, and //. Irviuscula muUisjnna). Abactinal 

 pseudopaxillse small, close-set, with few papillifonn spinelets to a group, these 

 groups arranged so as to form a close-meshed network; papular areas thus small 

 with one to three or four papulaj; marginal plates typically indistinct and small, or 

 not distinguishable from the other plates; when distinguishable they are small and 

 two series separated for part of length of ray by a series of small intermarginals; 

 adamulacrals with one spinelet in furrow, and on the surface upwards to fifteen 

 or, in very large examples, even more, spinelets ; of these, two or three large ones stand 

 on the furrow margin, forming an angular group and bcliind them the others very 

 abruptly decrease in length, those on outer part of plate being in a coordinate group. 

 (Typical Scandinavian specimens have fewer spinelets than these.) A single series 

 of actinal intermediate plates, except at base of ray, in large examples, where a 

 second row may be present. 



Variations. — The variations are legion and are bewildering. Some of the most 

 baffling varieties (so far as classification is concerned) I beheve are due to hybridi- 

 zation of what is here called sanguinolenta with aspera and multisp'ina and perhaps 

 also with leviuscula. One who has not been over the numerous specimens in the 

 collection can form no idea of the number of small and large deviations from the 

 type. It has not seemed feasible to name these variations because the specimens 

 are not constant enough to warrant it, and because it is more than probable that 

 some s[)ecimens are hybrids. A few of the j)rincipal varieties found in the collection 

 are listed below. 



Variety A. — Large size, nearly typical as compared with Scandinavian examples; 

 abactinal groups of spinelets small, with few spinelets to a group; marginal plates 

 not distinguishable except at tip of ray; adambulacral spinelets ten, those on furrow 

 margin heavy and slightly compressed at tip (stations 3561, 4803, and others). A 

 shght variation from tliis form has the spinelets with rather thick skin and the 

 marginal plates formhig very inconspicuous and not very regular series among the 

 other plates. They are noticeable by their larger size and more numerous spinelets 

 (station 4281 and others). (PI. 65, fig. 1.) 



Variety B. — Abactinal plates larger (more Uke small plated lexnuscula) with 

 twelve to fifteen spinelets; margmal plates easily distinguishable, a long series of 

 intermarginals being present (3214). A freakish looking variety possibly due to 

 hybridization with multispina; perhaps only an extreme of tlie next. 



Variety C. — Often very large; abactinal plates variable, either quite small and 

 close set with about twelve to fifteen slender spmelets, and two or three papulte, or 

 larger with about twenty shorter spinelets. Yet the plates appear small on account 

 of the large size of the specimens. The marginal plates are wide and conspicuous, 

 in regular series, a scries of small intermarginals extemling far along the ray; a 

 regular series of actinal intermediate plates for about half length of ray, a second 

 for about one-sixth, and sometunes a third on disk; marginal plates with numerous 

 spmelets, and the plates are more or less strongly compressed, so as to be much 

 wider than long, the spine-bearing portion forming a prominent keel; adambvilacral 

 plates with uj)wards to twenty-five or thirty spinelets. A ventral view reminds one 

 strongly of a very large leviuscula witli compressed marginals, while an abactinal view 



