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Show 430 PROF. F. 3. BELL ON PONTASTER TENUISPINIS. [May 17, The Duikers appear to be inhabitants of open or merely brush-covered regions, while the other Cephalolophi are for the most part inhabitants of dense forest, as m a y be judged from their extreme abundance in the West-African forest-region. 4. O n the Characters and Variations of Pontaster tenuispinis. B y P. J E F F R E Y B E L L , M.A., Sec.R.M.S. [Eeceived May 2, 1892.] (Pla'te XXVI.) In the year 1846 Diiben and Koren published their invaluable catalogue of the Echinoderms of Scandinavia, and since that time the species which they called Astropecten tenuispinus has been mentioned and more or less fully described by succeeding writers, such as Sars, Liitken, Koren and Danielssen. W e know now that the specimens seen by the famous zoologists who first described this species were all small examples ; two were quite small, having R equal only to 12 or 18 millim., while the third, with R equal to 45 millim., is much smaller than many specimens now known to us. The ratio of R to r is given by them as 4- 1 : but as r = 9 millim., when R = 4 5 , it is clear that the proportion varies from 4 or 5 to 1. The specimens described by Koren and Danielssen in 1884 were as much as 260 millim. in spread, and R = 1 3 0 and r = 23; or the proportion was as 5| (nearly) to 1. "With the variations in these proportions there must be some variation in the relative size of the disc and the general appearance of the specimen. Notwithstanding these differences, there has been a consensus of opinion among Scandinavian naturalists as to what should be called, as most of them call it, Archaster tenuispinus. Thanks to the obliging kindness of Prof. Loveu and Dr. Danielssen, I have been able to receive (and in most cases to keep for the British Museum) various specimens from various localities. Prof. Quennerstedt, of Lund, has been so kind as to compare specimens which I sent him for examination with the example on which Duben and Koren founded their species, not daring, rightly enough, to let the valuable specimen under his charge run any risk through the post. Having thus a considerable series of specimens before me, I find that the range of variation of ^ is greater than we have yet supposed, for r may be only 10 millim., and R=74 millim., or the proportion instead of being 4 or 5 to 1 comes to be 7f to 1. Mr. Sladen does not inform us what his ideas are as to Pontaster tenuispinis ; but he obviously looks on it as a small species, for he |
