256 
Darwin pointed out that his 7. serrata was more closely related to 7. forosa than to any 
other species. He would not, perhaps, have separated the two forms from each other as 
distinct species, if he had met with the specimens collected by the Siboga. They were found 
at the anchorage of Beo, Karakelang-islands (Station 131, July 24/25, 1899) when the reef 
was explored. 
The third lot of specimens belonging to this species is from the neighbourhood of 
Station 225. It consists of only two individuals: one loose, one attached to a piece of 
calcareous rock. The shape of these shells is conical, the colour greenish-grey. The surface 
is irregularly ribbed and shows the extremely narrow parietal tubes extending from the orifice 
almost to the base. The shape and structure of the opercular valves of these specimens corres- 
pond in general to those of the specimens of the other lots; yet the tergum has the spur 
relatively larger, and the curved carinal margin shorter than is the case in the other speci- 
mens. According to the label, this lot was taken near Station 225, 5700 m. to the N.E. of 
Southpoint of South Lucipara island. Here the depth was 894 m. The specimens of Zetra- 
clita porosa were not taken at that depth, but were found attached to a piece of coralline 
stone taken from the reef. 
2. Tetraclita costata Darwin. 
DARWIN, CH., Monograph. The Balanidae, Verrucidae etc. 1854. p. 339, pl. XI, fig. 2a—2e. 
Four to five small specimens of this species were found attached to a piece of stone 
collected on Banda Reef, at the end of November, 1899. Darwin knew it from the Philippine 
Archipelago, and WELTNER saw specimens from Larantuka. 
The specimens from Banda Reef are no doubt young ones. The greatest diameter of 
the basis of the largest specimen measured only 7 mm. 
3. Tetrachta vitiata Darwin. 
DARWIN, CH., Monograph. The Balanidae, Verrucidae etc. 1854, p. 340, pl. XI, fig. 3a—3e. 
A single specimen was collected on the reef of South Lucipara island. It has the irregular 
surface, the very irregular parietal tubes, and the moderately wide radii as in Darwi’s defini- 
tion of the species. The shape of the tergum and scutum is, moreover, exactly as in the figures 
given in Darwin’s Monograph. In the carina, some of the tips of the upfilled parietal tubes 
are exposed and these give a reddish-purple tinge to the uppermost part of that valve. The 
only specimen is medium-sized, the dimensions of the basis being 14 x 121/, mm., the ‘height 
measuring 7 mm. 
This species, which was described by Darwin from specimens from the Philippine 
Archipelago and from Barrier Reef (Raine’s Islet), Australia, was, according to WELTNER, 
collected also at Larantuka. The Siboga collected it on the Lucipara-islands (about Station 
225), which lie in the Banda Sea, during reef-exploration. 
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