1884.] species of oreaster. 77 



Oreaster dorsatus. 



Pentaceros dorsatus, Perrier, Rev. Stell. p. 245 ; but substitute 

 the following for the inexact synonymy there given : — 



1/53. Asterias dorsata^, Linnaeus, Mus. Tessin. p. 114, pi. ix. 2. 



1758. Seba, Thesaurus, iii. pi. v. 7, 8, pi. vi. I, 2. 



1766. Asterias nodosa, LinuEeus, Syst. Nat. p. 1 100 (joars). 



1842. Oreaster clavatus, M.Tr. Syst. Ast. p. 49. 



1864. Oreaster dorsatus, Liitken, Vidensk. Med. p. 161. 



This species has been so admirably diagnosed by Miiller and 

 Troschel that had I not here the object of giving original and 

 similarly constituted definitions of such species as I have seen, I 

 should gladly content myself with referring the student to their 

 description. 



Il=2'2r. Upper surface, in dried specimen, almost flat; arms 

 not acutely pointed. Lophial line and spines distinct, the apical not 

 especially prominent ; spines developed within the apical region. 



About 12 supero- and 14 inferomarginal spines, the latter distally, 

 but not proximally taking a share in the formation of the side of the 

 arm. Both sets are provided with spines ; on the upper plates these 

 spines are of some size, and frequently two are developed ; these are 

 set one above the other so as to lie at right angles to and not parallel 

 with the long axis of the arm. Two spines are likewise often 

 developed on the inferomarginal plates ; these spines are sometimes 

 of a fair size, but are frequently rather tubercular than spinous. 



Adambulacral spinulation diplacanthid ; three strong and often 

 subequal spines in the inner, and one very stout, with rounded tip, 

 in the outer row. 



The separate ventral ossicles are quite easily made out under the 

 rather coarse granulation by which they are invested ; the row of 

 ossicles running along the side of the adambulacral series is without 

 spines, but those outside this, of which there are four in the proximal 

 and two in the most distal region, are provided with one and some- 

 times with two rounded spinous projections. 



The upper, like the lower surface, is well provided with spines, 

 and here again two are frequently found to be developed on the free 

 surface of one and the same ossicle. The lophial ossicles are large ; 

 as large indeed, if not larger than, the more proximal superomarginals ; 



' The only foundation for the statement of Miiller and Troschel, reiterated 

 by Perrier, that in the Mus. Tessiu. Linnceus called tliis species A. stellata, is 

 the fact that the word stellata is the first in the definition of the species. As 

 the work is rare (the copy from which I took this note was one which I saw, by 

 the kindness of Professor Liudstrora, in the admirable Librarj' of the Royal 

 Academy of Sciences at Stockholm), I think it well to give in full what Linnjeus 

 said : — 



" JDorsata. Asterias stellata, radiis convexis longitudinaliter elevatis. Tab. ix. 

 fig. 2. 



Locus : India. 



Stella spithami diametro. Radii quinque, obtusi, versus basin dilatati, dorso 

 aduiodum convexi, adspersi undique mucronibus obtusiuseulis remotis. 



Subtus plana, adspersa punetis prominulis ; rima cincta papillis subulatis, 

 tenuissimis," 



