68 
PROCEEDINGS OF SOCIETIES. 
Before leaving the subject of dredging, I would wish to record the following 
note from Captain M‘Clintock, in reference to the naturalist’s dredge:— 
u My Dear Dr. Ball —Although we have left our ships and almost all our 
private property, as well as that belonging to the crown, behind us, yet the very 
small collection my other duties permitted me to collect with the dredge, I have 
brought home for you. There may be something of interest; and, according to Sir 
Edward Belcher, we have obtained some rare and new creatures. 
“ Although Sir Edward has devoted so many years of his life mainly to shell 
collecting, he was much struck with your little dredge; he immediately borrowed 
it, and had a larger one made of the same pattern. He confesses (and it is a great 
confession for him) that it is the best he has ever seen. 
“ Yours, very sincerely, 
u F. L. M‘Clintock.” 
The Genera Lacuna (except one species), Calyptrcea aplysia , Scrobicularia , and 
Donax do not range in our seas below this, the Laminarian belt, and Rissoa , 
Chiton , Bulla , Trochus , Mactra , Venus, and Cardium have the majority of their spe¬ 
cies within its precincts. 
A third region is the Median or Coralline Zone, occupying the spacebeen fifteen 
and fifty fathoms. In its upper portion, Trochus ziziphinus and tumidus, Chiton 
asellus, AcinEea virginea, Turritella communis, Venus ovata, and V. fasciata, 
Pecten opercularis, Modiola modiolus, the common form of Crenella, Pectunculus 
glycimeris, and Nucula nucleus, are characteristic testacea; and on its lower half, 
Solen pellucidus, Pecten varius, Dentalium, and Mactra elliptica. It is 
marked more by the peculiarities of its species than by the exclusive presence of 
genera. 
The fourth region is the infra median ; its most characteristic portions are in the 
extreme north. There are very few species of mollusca peculiar to it in our seas ; 
those that are found are, for the most part, of rather small dimensions, and 
remarkable for being of dull or pale colouring. Beneath this zone is the Abryssal 
region , which cannot be said to be developed within the British seas. 
Besides these several subdivisions of the floor of the ocean, there are the high 
levels of the sea-water itself, inhabited by a small assemblage of mollusks. The 
Genera Ianthina and Spirialis among our testacea, and our solitary species of 
Salpa, as well as the curious and anomalous Appendicularia among Tunicata, are 
inhabitants of this marine atmosphere; all these forms are, however, very local 
around our coasts. Bivalve mollusca would appear to be more extensively distri¬ 
buted in depth and to constitute more constant links between zone and zone than 
univalves. 
Having thus given some idea where the student will be likely to find the several 
genera and species of marine testacea, we must turn our attention to the 
Nudibranchs, or naked mollusca. These can be dismissed in a very few words ; 
they are chiefly to be found in rocky places, which, indeed, is the favourite locality 
for the majority of the Gasteropoda, and will be discovered creeping in the rock- 
pools, or upon the fronds of algae. Next in order we come to land shells, and 
there is not a place throughout the length and breadth of our country that some 
one species may not be found. The common Helix aspersa is a follower of cultiva¬ 
tion ; and where is the garden that cannot boast of the garden snail? Some of them 
prefer the sea-side, as Helix pisana, H. virgata, H. ericetorum, H. nemoralis, 
Bulimus acutus, and others ; some keep themselves strictly secluded to the chalk 
regions, as H. pomatia, H. carthusiana, Pupa secale, &c.; some hide themselves 
beneath moss, and it requires diligent search to find them, asH. pulchella, many of the 
Pupa and Zonites; others, again, climb to the tops of mountains, or love the retired 
recesses of deep woods, as Helix arbustorum ; endless are the situations in which we 
find the land shells, and few, if any, districts are without their fair proportion of them. 
The fresh-water shells are also found very widely distributed. In the swift¬ 
running streams Cyclas cornea will be found, with others of the same genus, and 
Ancylus fluviatilus holds hard to some large stone, braving most boldly the vigour 
of the stream. In ponds of stagnant water, Limneus palustris, truncatulus, Bithinia 
tentaculata, Planorbis corneus, and others will be found; while, again, up in a 
