288 bulletin: museum of comparative zoology. 



Asterias similispinis, sp. nov. 



Rays 5. R = 25 mm., r=5 mm., R = 5r. Iuterbrachial arcs acute. Rays 

 little flattened, upper surface somewhat convex, sides scarcely vertical, and actiiial 

 surface not sharply marked off. Breadth of ray at base 5.5 mm. Disc moder- 

 ate ; vertical diameter 5 mm. Whole abactinal surface quite closely and very 

 irregularly covered with low stout spines, which though blunt are not capitate ; 

 there are three or four of these spines to each square millimeter ; a median radial 

 line is seldom well marked. Papular areas very variable in size, with from one 

 to five papulae each. Among the spines are scattered small, rather stout and 

 blunt (less commonly, acute) pedicellariae. On sides of ray can be distinguished 

 a dorso-marginal and a ventro-margiual series of spines ; space between these dis- 

 tinct but narrow ; dorso-marginal series consists of a single (occasionally double 

 near base of ray) longitudinal row of spines simdar to and only a little larger 

 than those on abactinal surface ; ventro-margiual series made up of two rows 

 which are quite separate at base of ray but become very closely appressed as tip 

 of ray is approached, the lower spine of each pair being placed aboral to the 

 upper ; these spines are little longer than those of the dorso-marginal series, are 

 nearly cylindrical, and blunt ; near base of ray there may be two spines placed 

 side by side on each infero-marginal plate, in the lower row of the ventro-marginal 

 series. Most of the marginal spines of both series have a group of small pedicel- 

 lariae at the base, which, however, do not form a surrounding wreath. Adam- 

 bulacral armature consists of one or two large blunt cylindrical spines, very 

 similar in appearance to the marginals ; near base of ray every other plate bears 

 two spines, the outer one nearer the mouth, but at middle of ray and beyond, 

 most of the plates carry only a single spine ; all of the adambulacral spines carry 

 small pedicellariae, and there are similar pedicellariae on the plates within the 

 ambulacral groove. There are no spines between the ventro-marginals and the 

 adambulacrals, but no bare space is visible there, as the entire actinal surface is 

 covered by those spines. Oral plates each with two marginal spines at the inner 

 end, the innermost decidedly the larger ; a still larger superoral spine is present on 

 the surface of the plate near the middle. Madrepore plate free from spines, small, 

 1.5 mm. in diameter, situated about half-way betweeu margin and centre of disc. 

 — Color entirely bleached by alcohol. 



6 specimens, 23-45 mm. in diameter. Taraku Island, near Nemuro, Hokkaido, 

 Japan. Owston collection. 



It is only with the greatest hesitation that I venture to describe a new Asterias, 

 in the face of the large number of imperfectly described or little known species 

 which now make that genus a source of so much difficulty. But as the six speci- 

 mens before me agree in all essentials and differ in important particulars from any 

 of the species known to me, and most decidedly from any of the species hitherto 

 known from Japan (see Dbderlein's key to the Japanese species of Asterias, 

 Zool. Anz., 25, p. 331), I have felt justified in giving them a new name, based 

 on the remarkable similarity between the adambulacral and marginal spines. 



