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THE VOYAGE OF H.M.S. CHALLENGER. 
axis of growth) and broad ; curved or irregular in outline ; subdivided more or less 
completely by numerous secondary septa. Walls rough externally, interior surface 
smooth. Aperture porous. Diameter of the adherent patches -jttli inch (4 mm.) or more. 
Bdelloidina aggregata is generally met with in the form of little, grey, sandy, 
spreading patches, growing on fragments of shell or coral, usually selecting some 
hollow or cranny, where it is protected by its position from external injury. Under the 
microscope it is found to consist of a more or less complicated mass of segments, arranged 
in somewhat irregular, broad, either simple or divided lines, often a good deal crowded 
together. 
The segments are long and very narrow, and are placed side by side, so that their 
length lies transversely to the axis of growth. Owing to the nature of the bottom in the 
localities which the organism affects, the test is usually constructed of calcareous rather 
■ than siliceous sand. The exterior is rough, and the sutural lines distinct and slightly 
excavated. 
The cavities of the chambers are irregularly divided by transvere partitions, as shown 
in fig. 6 ; but the subdivisions of the adjacent chambers do not correspond in size or 
position, nor are they indicated in any way on the exterior of the test. The interior 
surface is smooth, and is marked by punctations which have the appearance of large 
pores. A very similar condition is presented by the inner surface of the shell of 
Trochammina trullissata (PL XL. fig. 16). In that species it can be easily demonstrated 
that the test is not really perforated, and that the markings only represent a very early 
or rudimentary condition of the cancellated structure which finds its fullest development 
amongst recent types in the genus Cyclammina ; and as no pores are visible externally 
in the test of Bdelloidina, it is probable that in Bdelloidina also the puncta on the 
internal surface are mere superficial depressions. 
The general aperture of the test is very distinctive : following the common rule of 
labyrinthic Foraminifera, it is cribrate or porous, and takes the form of a single row of 
round orifices on the outer face of the terminal chamber, as shown in figs. 4 and 5. 
Bdelloidina aggregata is manifestly a rare species. The Challenger specimens, 
which are few in number, were all obtained from two or three dredgings in shallow 
water near the Admiralty Islands, on the north coast of Papua, and they are generally 
adherent to fragments of molluscan shells. Mr. Carter gives no locality for those which 
form the subject of his paper, but states that they were found “ in excavations on the 
surface of a large globular mass of Siderastrcea.” 
Prof. Rupert Jones has for many years had in his possession a characteristic drawing of 
this species, taken from a fine specimen adherent to a Cretaceous Ammonite in Mr. 
Matthew Wright’s cabinet. Probably the examination of the surface of Mesozoic fossils 
would bring to our knowledge other examples of this sort. 
