430 PROF. F. J. 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 may be judged from their extreme 

 abundance in the West-African forest-region. 



4. On the Characters and Variations of Pontaster tenuispinis. 

 By F. Jeffrey Bell, M.A., See.R.M.S. 



[Eeceived May 2, 1892.] 



(Plate XXVI.) 



In the year 1846 Diiben and Koreii 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. 



We know now that the specimens seen by the famous zoologists 

 wiio first described this species were all small examples ; two were 

 quite small, havuig R equal only to 12 or 18 miUim., while the 

 third, with R equal to 45 millim., is much smaller than many speci- 

 mens now known to us. 



The ratio of R to /• is given by them as 4= 1 : but as '/•=9 millim., 

 when R=45, 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=130 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. Loven 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 Diiben 

 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 sup- 



K 



posed, for r may be only 10 millim., and R=74 miUim., or the 



proportion instead of being 4 or 5 to 1 comes to be 7f to 1. 



Air. Sladen does not inform us what his ideas are as to PoiUaster 



tenuispinis ; but he obviously looks on it as a small species, for he 



