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Show 1892.] PROF. F.J. BELL ON PONTASTER TENUISPINIS. 431 says of a variety that its " habit " is much larger than that of " examples which I have seen of the type-form." The largest of his varieties appear to have R = 6 6 , but Koren and Danielssen had examples of P. tenuispinis in which R=130. However, it is useless for anyone who has not, like myself, access to the collection which Mr. Sladen describes, to hope to discuss with him any question which is based on measurements, for of these no writer is so chary. The proportions of R to r in this variety of Mr. Sladen's vary from 3 ^ , through 344{ and 4 to 4 ^ and 4f ; as the variability is so great, I consider the relation of R to r should be put aside as a reason for distinguishing a variety of a form which itself shows a variation between 4 and 7-|. The original diagnosis of the species begins with the words" radiis attenuatis"; but in this point I observe some differences among the specimens, some of which have arms a good deal stouter than others. But on this point it is necessary to be precise, for Mr. Sladen's variety, which he calls "platynota"1 (a misprint, I presume, for A A B Diagram showing the relative proportions of the arms of (A) P. tenuispinis and (B) P. platynotos. platynotos), is said to be marked by a " rapid attenuation " of the rays at a short distance above their base. If figures can be made to prove anything, words may be taken to mean anything ; and a " rapid attenuation " may mean anything between the loss of weight which follows a few days' hard exercise or the result of a ten-weeks' bout of fever. measurement, w eW fhiendn twhaet bornien ge xthaimsp vlaeg uoef etxhper evsasriioent yt oh atsh ea nte satr omf 1 Ohall. Eep. Asteroidea (1889), p. 29. 30* |
