NARRATIVE OF THE CRUISE. 
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adamsii, see fig. 210) was also obtained at a great depth (2450 fathoms) in the Atlantic, 
southwest of Sierra Leone. Yet this genus does not always dwell in such deep water, for 
the typical species ( Callocardia guttata) was dredged by Arthur Adams off Quelpart, 
south of the Korea, at a depth of only 48 fathoms. As might be expected, the deep-water 
forms present no colour-markings, but in Callocardia guttata a few pale orange spots are 
scattered over the surface. 
It is a curious fact, that, as far as the collection of Lamellibranchs has been studied, 
although the number of new species is very considerable, only a single new generic form 
has been discovered. This is contrary to one’s expectations, and even among the few 
species dredged at depths exceeding 2000 fathoms I do not find one which we might not 
have expected from 100 fathoms or less. The new genus Silenia was obtained from 
2650 fathoms, two Areas from 2050 and 2150 fathoms, a Malletia from 2550 fathoms, 
and a Lima from 2500 fathoms, genera of which species are already known from less 
than 100 fathoms, and indeed in the case of Area and Lima from low-water mark. 
Although the genera have such a, wide bathymetrical range, of course it does not follow 
Fig. 210 . — Callocardia adamsii, n. sp. Station 348, Fig. 211 . — Nuculina ovalis, Searles Wood. 
2450 fathoms. Enlarged. Simon’s Bay, Cape of Good Hope, 15 to 
20 fathoms. Ten times the natural size. 
that the species will always exhibit a similar distribution. In some cases, however, this 
is known to occur, and it will no doubt be discovered in many more. As an instance 
of this I may cite the well-known Ervilia castanea, which may be dredged in less than 
50 fathoms off Great Britain and elsewhere. Specimens of this species were obtained by 
the Challenger in 450 and 1000 fathoms off the Azores, agreeing precisely with shells 
from shallow water, Cryptodon jlexuosus and Cryptodon croulinensis respectively, from 
450 fathoms and 1000 fathoms off the Azores may also be got in British seas in less 
than 50 fathoms. I was in hopes that certain types which at present are known only 
in a fossil state, might still have been found existing at great depths. The discovery 
of some of the remarkable forms of Trigonia, Pholadomya, and other genera which 
abound as fossils have been hoped for in vain. One interesting occurrence, however, of 
a species in a living state hitherto known only from the £ crag,’ is worth recording. 
The little Nuculinaovalis of Searles Wood (see fig. 211) was brought up from a depth 
