626 
THE VOYAGE OF H.M.S. CHALLENGER. 
of only 15 to 20 fathoms in Simon’s Bay off the Cape of Good Hope. This is not, 
however, the first record of the genus as recent, a species from the Catalina Islands 
and another from the Korean Straits having already been described. 
“Judging from this collection, the conclusion may be drawn that forms from very 
deep water, as a rule, have thin shells and are devoid of colour. As an instance of this 
I may cite a very beautiful species of Modiola from Stations 191 and 207. The 
specimens from the first locality, dredged in 800 fathoms, besides being very fragile, are 
totally white, those from Station 207, from 700 fathoms, being faintly tinged with olive 
on one side, showing a return to the usual olive or brownish tint which mostly prevails 
in species of this genus. Among the prizes of the Expedition are one or two very 
beautiful forms of Amussium from depths exceeding 1000 fathoms. Unlike the type 
of the genus, Amussium pleuronectes , these are excessively thin, semitransparent, and 
Fig. 212 . — Amussium watsoni, n. sp. Station 
218, 1070 fathoms. Natural size. 
Fig. 213. — Area corpulent a, n. sp. Station 184; 
1400 fathoms ; Station 194, 200 to 360 fathoms ’ 
Station 198, 2150 fathoms ; Station 216a, 2000 
fathoms; Station 271, 2425 fathoms; Station 
300, 1375 fathoms. Natural size. 
destitute of colour, but a species dredged off the Philippine Islands in 375 fathoms, 
although equally fragile, has the central portion of the valves of an orange tint. 
Among the species of Area are a few from very great depths which have comparatively 
thin shells, hut which maintain the fibrous character and usual colour of the epidermis 
prevailing in many well-known forms found in shallow water. 
“ From the above notes it will therefore be seen that the abyssal fauna of the ocean, 
so far as the Lamellibranchiata are concerned, does not apparently (judging from the 
Challenger collection) differ greatly in the known generic types from that of shallower 
seas. The species met with in very deep water may- have been gradually modified from 
those living nearer shore, and become scarcer through inhabiting regions where food is 
less abundant and the general conditions of existence less favourable.” 
