93 
Report on the Microscopic Structure of Shells. Part II. 
By William Carpenter, M.D., F.R.S., F.G.S. 
(Continued from Report for 1844, p. 24.) 
hitroducionf Ranarh. 
In my former Report I gave an account of the principal varieties of elemen¬ 
tary structure, which had presented themselves to me during a mitiute and 
extensive examination of tJie shellsof MoUusks; and I described the peculiar 
eoTohinalions and arrangements of these elements, which are characteristic 
of the following ^ups of Bivalves, namely, the Braekiopoda, the Ptneunida, 
O^racea:, Ptitinida, SfargarUacea: and S'ayadviv. On the present occasion 
I shall enter into similar details in regard to the remaining faniUifa of the 
LameUihranckiata \ and shall state the results of uiy inr^uiries into the 
^eture of the shells of the Gasteropoda ami Cepltalajtoda. These last an;, 
however, chiefly of a negative character. 
Ilefore proceeding, however, to this continuation of tny former Report, I 
shalt make a few additions to the facts contained in it, as to the structure of 
“e shell in certain of the groujjs therein described, which have resulted from 
the coDtlnoation of my inquiries into their organic peculiarities. 
I. Obserrations Sifpplemmlul to farmer Report. 
57. £mcA/(^a,_When drawing ntlenlion (§ 41) to the very rcinark- 
ay system of perforations presented by tJ»e shells of ctJrtain species of Te- 
rdnabilu and allied genera, 1 was obliged to express iny ignorance of the 
re abon which these passages have to the structure and ccconomy of the 
Mima ; not having had at that time the opportunity of examining a shell, the 
been preserved in situ. This opportunity, however, by 
kindness of Mr. Cuming and Mr. MacAndrew, I have since enjoyed ; 
anc 1 can now eomiTmnicatc tlie results of my inquiries, which, though not 
fouud, f tliink, to jxjssess much interest. 
OB. 1 he species on which niy observations have been made, are the T. 
rails, and the 7\ mpui serpentis (?) lately discovered to bo a native 
our own sea^. When a thin portion of a sliell of cither of these (and 
h u ^ of am/ of the perforated species of 'I'ercbratuhi) wliich 
preserved with the animal in spirit, is ground down from the inner 
the outer surface unchanged, it will be seen that each 
1 oiulioii in the shell is cevered-in by an oval membranous disc, wliosc 
ure appears very firm (fig. 1 ). When .u thin section thus m:ulc is ex- 
^ to the action of dilute acid, so a? to remove from it the calcareous 
pj. Men that lluwe. discs are connected together by a layer 
out DitJH'brane, in which no distinct structure can be made 
L i - _ this membrane, diffiTing as it does from the membranous 
liffht f 'Jiterior layers of the shell, is probably to bo rcgariled in the 
nes.L When a portion of the shell, not reduced in thick- 
^°™P*®tely decalcified by inioiersiou in dilute acid, and the mem- 
its^lf'**' ^®*hluuni is then examined, a vmy remarkable structure presents 
tariiwlT Laniellibranchiate Bivalves. At- 
RMinH! “’^™hranou5 fibns are a series of tubular appendages, corre- 
i thametor to the perforations in the shell, and arranged at the 
hroff ti "fhe/rw extremities of these appendages are mueli 
OUtinpt attached to the membrane, imd have 
cacal terminations, which appear by the straightness of their border 
