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Turbinaria). The new species from the Malay Archipelago, which will be described in this 
report, are also inhabitants of shallow water. 
According to Darwin, Acasta is always embedded in sponges, or in the sponge-like 
outer layer of the skeleton of /s¢s. ANNANDALE took his new species from the surface of Zz7- 
binaria, a Madreporarian coral. Krtcer does not inform us from what host his new 4. Doflecnz 
was taken. WeELTNER’s A. scutecosta was found living in a sponge: Zethya lyncurtum Johnst. 
GruveL, with regard to his new species, A. strzata, only says that it was “ramenée d'une 
profondeur de 400 métres”. With regard to the Siboga-species, 4. glans from Pepela-Bay, 
Rotti-island, was handed to me disengaged from the sponge in which, presumably, it was 
originally found embedded; the other specimens of this species, which were collected by the 
Dutch Fishery Inspection-Steamer “Gier’’, are still partly covered by pieces of sponge. A. conica 
n.sp. came into my hands with the sponge in which it is embedded. The surface of the latter 
shows almost quite globular excrescences, with a small oval opening at the tip, and the Acasta 
is found in this excrescence, the aperture of its opercular valves corresponding exactly to the 
opening of the sponge. The specimens of 4. xztida n. sp. were taken out of the sponge 
and even quite clean when they came into my possession. 
A few words may be said here on the peculiar position of the genus <Acasfa in 
the classification of the Sessile Cirripedes. Darwin considered it as a Sub-Genus, without 
saying exactly what he meant by that term and ‘“hoped’’ he might stand excused for 
admitting it as such. According to him the species of this genus, in the structure of the 
shell, and in all the characters derived from the opercular valves and animal's body, cannot 
properly be distinguished generically from some species of Aa/anus. He pointed out that 
some species of the latter genus (2. xavicula and B. cymbiformis) agree in all essential 
respects with Acasta, and differ only in the shell being more elongate and in being attached 
to Gorgontae instead of to sponges; Acasta purpurata, however, lives embedded in the 
outer layer of the skeleton of J/szs, so that even the habit of living embedded in sponges 
fails in that species. There are, on the other hand, species of Balanus (BL. spongicola, 
4. dechvis) that inhabit sponges .... Darwin finished by saying that the most important 
character of Acasta probably consists in the anterior ramus of the fourth pair of cirri 
differing slightly in the arrangement of its spines, and in some other points, from the rami 
of the posterior pairs of cirri, and considered this’ as a character not as yet observed in any 
other Cirripede. 
As I pointed out when discussing the difficulties of subdividing the genus alanis, 
this very same character is observed, however, in further species of Aavanus, and, certainly, 
the validity of the genus Acasta has not been strengthened by this discovery. But, on the 
other hand, the present known species of Acasfa seem together to form a very natural group, 
characterized by the thinness of the parietes in which pores are absent, by the great develop- 
ment of the radii, by the cup-formed basis and by their living — with a single exception — 
embedded in sponges. Therefore I would not consider it an advantage to cancel this genus 
and to include its species in the genus 4alanus, however closely related the two genera 
may be. Perhaps a thorough study of sufficiently rich material of those species of Lalanus 
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