Bd. VI: 4) 
THE ECHINOIDEA. 
59 
In 1 88 1 Prof. Bell described, in his Report on the Echinoderms collected by 
the »Alert» in the straits of Magellan and on the coast of Patagonia (Proc. Zool. 
Soc. London i8Si, p. 88), a new species of Strongylocentrotus , named Sir. bullatus. 
In discussing its relation to the other species of the genus Bell points out that »it 
seems to be the only species in which all the ocular plates are excluded from the 
anal system — presenting a considerable resemblance to S. franciscanus , in so far 
that the primary tubercles of the interambulacral areæ form, in both species, two 
rows, and are considerably larger than any others on the test So, again, 
a resemblance is to be seen to S. albus in the presence of the tubercles separating 
the arcs of pores; but these tubercles are much smaller and much more irregular in 
S', bullatus, and this new species has also a somewhat larger mouth (actinostome)». 
In spite of the differences here pointed out I must regard bullatus as a synonym 
only of albus. Regarding the ocular plates there is, as has been shown above (p. 54), 
so considerable a variation that no reliable specific difference can be found in the re- 
lation of these plates to the periproct. The size of the tubercles separating the arcs 
of pores is likewise too variable to be relied upon, and likewise I cannot agree that 
they are more irregularly arranged in » bullatus » than in albus. Finally the size of 
the actinostome! On p. 425 — 26 of his paper »Observations on the characters of 
the Echinoidea IV. The Echinometridæ» (Proc. Zool. Soc. 1881) Bell gives some 
measurements of specimens of both species, one of each being 115 mm. in diameter; 
the percentage value of the actinostome for these two specimens is given as 20.9 in 
albus , 23.04 in bullatus; in the other specimens the percentage value of of the actino- 
stome is calculated to 21.9, 24 and 27.4 for albus , 30.8, 31.6 for bullatus. For the 
specimens of which the measurements are given above (p. 53) the percentage value 
of the actinostome becomes: 25.05, 28.35, 30.42 and 22.13. This shows that the size 
of the actinostome is also too variable for being used as distinguishing character. 
The specimens measured here show the same range of variation in regard to this 
character as both the »species» of Bell — and that these specimens are really all the 
same species, can in no way be doubted. The distinguishing characters pointed 
out by BELL between albus and his species bullatus are thus irrelevant, and I am 
unable to find any better ones. Also the pedicellariæ are alike, as I have stated in 
the »Ingolf» Echinoidea I. (p. 123). (Regarding the small form of tridentate pedi- 
cellariæ described from »Sir. gibbosus » (= L. albus) in this place, cf. above p. 55.) 
The colour of the test of bullatus , it is true, is described by Bell as »brownish red», 
which is not in accordance with the characteristic colouration of albus described above 
(p. 55). The reason of this difference, however, is no doubt to be found in the 
fact that Bell’s specimens have been dried without having the skin cleaned off, 
which is rather thick and brownish pigmented. — The result is that Bell’s Stron- 
gylocentrotus bullatus must be regarded as a synonym only of Loxechinus albus; 
