64 BULLETIN 84, UNITED STATES NATIONAL MUSEUM. 



AMPHIURA STIMPSONI LUtken. 



Plate 7, figs. 1-2. 



Amphiura stimpsoni Lutken (59), p. 116. 

 Amphiura stimpsoni Ljungman (66), p. 320. 

 Amphiura stimpsoni 'LjviiG'M.Ai^ (71), pp. 631-634. 

 Amphiura stimpsoni Lyman (75), p. 4, pi. 5, fig. 66. 

 Amphiura stimpsoni Lyman (82), pp. 124-143. 

 Amphiura stimpsoni Lyman (83), p. 252. 

 Amphiura stimpso7ii Marktannek (87), p. 299. 

 Amphiura stimpso7ii S.. L. Clark (01), p. 247. 



Key West. Six specimens. 



In one of these specimens the diameter of the disk is about 4 mm. ; the others 

 are smaller, the diameter of their disks being comprised between 3.5 and 2 mm. 



I have been able to compare with these two specimens the two examples in the 

 Copenhagen Museum which were used as types by Lutken and which were most 

 kindly communicated to me by Doctor Mortensen ; I have ascertained their agree- 

 ment, excepting very slight differences in the shape of the mouth shields. In 

 Liitken's two specimens, the mouth shields are almost triangular, as long as wide, 

 ^\-ith a fairly sharp proximal angle and a very convex distal side. In my own 

 specimens, I sometimes observe the same shape, but most often the proximal angle 

 is obtuse and rounded, as is the case with the sample photographically reproduced 

 in pi. 7. These shields always remain as long as wide, or sometimes they are very 

 slightly wider than long. The brachial spmes amounting to five, are rough, as 

 stated by Liitken, and I find that the small rugosities have even a tendency to 

 develop a little at the end of the spines, and more so on the second ventral one. 



Among the authors who, after Lutken, have given some indications regarding 

 A. stimpsoni, I can quote only Lyman and Marktanner, but the information given 

 by these two writers is not in accordance with Liitken's description. Lyman 

 published (in 1875) a scheme of the imder face on which the mouth shields are repre- 

 sented with a very elongated oval shape; moreover, Marktanner writes that the 

 two dorsal spines have a little aboral hook and that the mouth shields are cordiform, 

 a little longer than wide. Now, these characters, it is evident, do not agree with 

 those observed by me, not only on my own specimens, but on Liitken's two examples, 

 and, in particular, the shape of the mouth shields as represented by Lyman, is 

 altogether incorrect; I am in doubt whether the two above-named writers dealt 

 with the same species. 



Lutken suggested that A. stimpsoni was a yoimger form; this is qiiite possible, 

 but I do not see to which of the known AmpJiiurse of the West Indies it might 

 correspond. I have compared my examples with very young A. Tcukenthdli, gathered 

 at St. Thomas by Messrs. Kiikenthal and Hartmeyer, and I fuid that the latter 

 possess two tentacular scales, wider upper brachial plates, stronger mouth shields, 

 and their second ventral spine at least already bears its characteristic hook; 

 moreover, the mouth shields have a different shape, for they are elongated and 

 pyriform. Evidently A. stimpsoni does not represent a younger form of A. 

 Icukenthali. 



One might also compare A. stimpsoni with the AmpMura which I have described 

 above imder the name of A. fiiulata, taking as a basis the fact that the latter has 



