Xvi PERCY SLADEN TRUST EXPEDITION. 
the details also appeared of Dr. John Anderson’s collections in the Mergui Archipelago, 
the Echinoidea being described jointly by Duncan and Sladen (35), and the Asteroidea 
by Sladen alone (19). No new species were discovered, but some interesting light was 
thrown on problems of geographical distribution, the distinctness of the Mergui and 
Andaman faunas being especially noticeable. Two years later (1891) we find Sladen 
reporting on a collection of Echinodermata from the South-west coast of Ireland (21), 
in which several new species were discovered ; and in 1887 he gave a list of Echinoderms 
dredged in the neighbourhood of Rockall Island (23); while at the time of his death he 
had in hand the collections from the ‘ Albatross’ expedition. 
With his time so fully occupied by systematic work, it is not surprising that he 
contributed but little to our knowledge on more general problems. His articles on 
pedicellariz (8) and on the ancestral relations of Asteroidea and Ophiuroidea (10) have 
already been mentioned ; and the only other paper which is not directly concerned with 
classification is that ‘“‘On the Homologies of the Primary Larval Plates in the Test of 
the Brachiate Echinoderms” (16), published in 1884. In this he supported his friend 
P. H. Carpenter, and his main conclusions will probably be accepted by most students 
of the subject; though it may be questioned whether either of these authors made quite 
enough allowance for the effect of homoplasy, on structures which are bound to be 
affected by the general pentamerous symmetry. 
Besides these numerous publications on recent forms, Sladen was responsible for a 
number of paleontological works, some undertaken alone, and others in conjunction 
with P. Martin Duncan. Of his independent papers, those on Potertocrinus (1) and 
Lepidodiscus (5) have been already alluded to; but far more important was the mono- 
eraph on British Cretaceous Asterids (20), which he took over at the request of the 
Paleontographical Society on the death of Dr. Thomas Wright. Unfortunately he 
only lived to complete two parts, though he left manuscripts and plates nearly 
ready for publication, and these were placed after his death in the able hands of 
Mr. W. K. Spencer, who is now engaged in completing the monograph. 
Among the papers written with Duncan’s help the two beautiful monographs published 
in * Palezeontologia Indica’ stand out prominently as of first-class importance. One of 
them (27) deals with the Echinoidea of Sind, and was published in six parts between 
the years 1882 and 1885; while the other (28) describes the Tertiary Echinoidea of 
Kachh (Cutch) and Kattywar. Out of the former arose a slight controversy with 
Prof. Lovén, who at first expressed the opinion that Heméaster elongatus, a common 
fossil in the Ranikot Series of Sind, was a form of Pal@ostoma. Duncan and Sladen, 
however, ina separate paper (29) so completely vindicated their position that Prof. Lovén, 
with characteristic frankness and courtesy, admitted that he had been inerror*. Out of 
the description of the Sind fossils arises another short paper (33) in which certain forms 
transferred by M. Cotteau to the genera Pseudopygaulus, Trachyaster, and Ditremaster 
are restored to Holampas, Duncan and Sladen, and Hemiaster, Desor. Other works of 
minor importance by these two authors are: a description of the Arbaciadze (30), dealing 
* Sce Ann. & Mag. Nat. Hist. ser. 5, vol, xv. p. 72. 
