ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHER. 287 



Adambulacral plates with typically twenty-fivo to forty (soniotimos iis nianv 

 as fifty or as few as twenty according to size of sjjecinu'n) multidenticulate spinelots, 

 those on outer part of pliite similar to the actinal intermediate spinelets in size, 

 and increasing; in lenf^tli and tliickness toward furrow, on the mar<rin of which are 

 about three or four stout often compressed sj)inelets. The spinelets are in four to 

 six not very rejjular transvei-se series on outer part of plate, and three or four on 

 inner. A characteristic of this form is the presence of two furrow sj)inelets (one 

 above the other) on the furrow face of the plate, on outer third, half or two-thirds 

 of ray; proximally there is but a sinjile spinelet, as in //. levluscula. In some 

 intermediate or aberrant examples the diplacanthid plates are confined to the tip 

 of ray. No typical examples lack them, however. 



Madreporic body slightly convex, circular, of very variable sculpture, but 

 covered with small spinelets similar to those of the adjacent plates. 



Color in life. — A specimen from station 4791 was colored in life as follows: 

 Central aboral rep^ion pale lilac, fading; toward and disappearing near midille of 

 arms; other parts creamy, more yellow toward tips of arms (J. O. Snyder). 



Variations. — The typical examples of this species or race (wliichever it is) are 

 so different from levluscula that thej' may be told at a glance. But the deviations 

 from the type are both varied and numerous, so that it is sometimes impossible to 

 decide how a given specimen should be classified. Whatever may be the explana- 

 tion of the midtitude of variations it is certain that the i\Jaskan specimens present 

 the extreme of difference from lei-iuscula,vfh\\o the Californian race, rfi/scn'to. forms 

 a fairly perfect connecting link. Dyscrita has much fewer than the typical numbei- 

 of adambulacral spinelets (usually fifteen or less), fewer and shorter spinelets 

 to the abactinal plates, and two spinelets on the furrow face of the adambulacrals 

 only at tip of ray and sometimes not at all. Certain extremes of levluscula froni 

 tide pools of Monterc}- Bay are so close to extremes of this southern representative 

 of multi-splna that it is well-nigh impossible to separate them. One is forced to 

 conclude that the two forms really intergrade. It is possible that muUispina is a 

 deeper water variety or race of levluscula, and there is also evidence that the more 

 delicately spincd forms are from soft bottom while the short-spined anomalies, so 

 difficult to classify satisfactorily, are the same species or race from hard bottom. 

 However, multlspina is found along shore, for there are several specimens from 

 Kadiak Island which are nearly like the typical form. From here also are a number 

 of specimens which depart from the type antl approach levluscula, and a very few 

 which are intermediate. They were evidently collected along with typical hviuxcula 

 and presumably occur together (see Kadiak variety below). Still another possi- 

 bility is that muUtsplna is a distinct but variable species wliich encroaches upon 

 the domain of levluscula (which occui-s from low tide to moderate dejjths) ami that 

 whenever this occurs hybridization takes place more or less frequently. Ii\ this 

 manner some of the freaks might have originatetl. The probability of hybridism 

 is verv strong in the case of asptra and leviu.scula. When two well-marki'd forms 

 range together it often haj)pens that spccinu-ns are found whicii are more or less 

 mosaics of these. Such aberrant forms are bewilderingly variable. Some of the 

 more important variations arc noted below. 



