Xii PERCY SLADEN TRUST EXPEDITION. 
his own untiring energy and ability, he soon acquired that thorough general knowledge 
of his subject which is the indispensable preliminary to original research. 
Sladen’s first paper (1) appeared in the ‘ Proceedings of the Geological and Polytechnic 
Society of the West Riding (Yorkshire) ’ in 1877, and dealt with the genus Poteriocrinus. 
After enumerating the various species hitherto attributed to it, he showed that they 
fell readily into several groups, and proposed to distribute them over four genera, of 
which one (Dactylocrinus) was new. In the same year he visited Naples, where he 
worked for several months at the Zoological Station; and it was there that he made 
the observations on Pedicellarizw, of which he afterwards published an account (8) in 
the ‘ Annals and Magazine of Natural History.’ There, too, he received from Madagascar, 
in a dried state, the only known example of that extraordinary form which he named 
Astrophiura permira. His first paper on it was read before the Royal Society in June 
1878 (2); but as only an abstract was printed in the ‘ Proceedings,’ he published in 
the following year a specific diagnosis in the ‘ Zoologischer Anzeiger’ (3), and a fuller 
description, with figures, in the ‘Annals and Magazine of Natural History’ (6). He traced 
with great skill the points in which it resembles the Ophiurids on the one hand and 
the Asterids on the other, and concluded that it must be placed in a new family 
(Astrophiuridz) intermediate between the two classes. Besides these three papers this 
species is also responsible for a fourth, published in the Proc. York. Geol. & Polytech. 
Soc. in 1881 (10), in which Sladen put forward some novel views as to the homologies 
of the various plates in the arms of Ophiurids and Asterids, making good use of the 
intermediate position of Astrophiura *. 
At the close of 1877 appeared the first of a long series of papers in which Sladen 
collaborated with P. Martin Duncan, who, having received for description the Echinoderms 
collected by H.M. ships ‘ Alert’ and ‘ Discovery’ in the Polar Seas, handed them 
over to Sladen for independent examination. Their preliminary report (24) was 
published in 1877, and was followed in 1881 by a complete memoir (26) in which are 
given some interesting observations on the geographical distribution of the Arctic 
Echinoderms ; and it is shown that they are not forms which have spread northwards 
from the nearest temperate seas, but belong to a distinct circumpolar fauna. 
Only one new species resulted from this expedition, and that, as expressly stated in 
the preliminary notice, was discovered by Sladen. At first he named it Asteracanthion 
paleocrystallus, but subsequently, recognising that it belonged to the rare genus 
Pedicellaster, Sars, he published a separate paper on it (7) under the name P. paleo- 
erystallus. This name is retained both in the complete “ Memoir on the Echinodermata 
of the Arctic Sea” (26) and in the ‘Challenger’ Report (18); in the latter, however 
(p. 560), notice is taken of Danielssen and Koren’s objection that it is identical with 
P. typicus, which Sars had imperfectly described. Sladen, while still maintaining the 
distinctness of the two forms, expressed the intention of making a further examination, 
but it does not appear that he found opportunity to do so. 
* It is a matter of profound regret that this unique specimen is lost. Some time after Sladen’s death his 
collectious were presented by his widow to the Royal Albert Museum at Exeter ; but the Curator, Mr, F. R. Rowley, 
after a most careful search, was unable to find any trace of Astrophiura, 
