82 REPORT—1846. 
aspera, and Ebalia Pennantii, require only to be enumerated. Xantho rivulosa, re- 
cently discovered to be a British species, is also included. In addition to Pagurus 
Prideauzii, I find also two of the new species of Pagurus, which J have recently de- 
scribed; of these two, P. /evis was first discovered by Mr. Thompson on the Irish 
coast; the other was found off Plymouth by Mr. Cocles, and first described by me 
under the name of P. Forbesii. Lithodes arctica, a northern form, is also in the 
present collection ; but the most interesting amongst the fruits of this little expedi- 
tion is a fine specimen of a species of the natatory type of the Brachyura, a Portunus 
entirely new to our fauna, and which appears to me to be P. longipes of Risso, a 
Mediterranean species. It differs from the only specimen I have in my collection 
of the latter species, but this may arise from my Mediterranean specimen being very 
young. 
On the Structure of the Pycnogonidee. By Dr. CARPENTER. 
The President exhibited a specimen of a beetle (Blaps mortisaga), which has been 
found imbedded in some artificial concrete, where it must have been at least sixteen 
years; and yet, when the animal was brought to him, it was alive, and lived for six 
weeks after. 
Dr. Carpenter gave an account of his researches on the microscopic character of 
shells, and also the results of his attempts at representing natural history objects by 
means of photography. 
On the Dissimilarity in the Caleifying Functions of Mollusks, whose organi- 
zation is in other respects similar. By L. Rerve, F.L.S. &e. 
Each of the four shell-secreting kinds of Cephalopods—the Cuttle-fish, the Paper 
Nautilus, the Pearly Nautilus, and the Spirule or Ram’s Horn—exhibits a different 
method of forming its shell,(this shell differing in microscopic structure, and secreted 
from different parts of the system,) although strictly allied in all those elements of ana- 
tomical detail which constitute the soft parts or animal frame. Whilst the calcareous 
portion of the Cuttle-fish is merely represented by an internal bony plate, consist- 
ing mainly of carbonate of lime, the shell of the Pearly Nautilus constitutes a huge 
mechanical apparatus, secreted from the mantle enveloping the visceral mass, and 
consisting of two separate deposits—an outer crust, and an inner nacre—for the 
purpose of buoying up its inhabitant under the different mutations of pressure to 
which it is subjected in its deep region of habitation. The shell of the Paper 
Nautilus, on the other hand, is a light elastic boat, transparent and permeable to 
light, secreted only by the female for the purpose of oviposition ; and in this animal 
the office of calcification is transferred, by some mysterious order, from the mantle to 
the hinder pair of arms. The Spirule is again totally different, it being contained 
within the mantle of an animal, far larger, in proportion, than that of the other Ce- 
phalopods, under circumstances which are at present unknown. The drawing exhi- 
bited was taken from a living specimen, recently collected at New Zealand, by Mr. 
Earl, for the first time in perfect condition; but, as the proprietor is unwilling that 
it should be dissected, Mr. Reeve could only state that it enclosed a problem in the 
physiological history of the Cephalopods, which it was extremely desirable to solve. 
The next point to which he directed the attention of the Section was the curious 
difference which occurs in the growth of the Cowry and the Olive; but this he had 
already more fully communicated to the Linnean Society. 
On certain Peculiarities in the Anatomy of Limax Sowerbii. 
By Prof. Attman, ILRLA. 
The peculiarities of structure in this animal are chiefly to be found in the repro- 
ductive system, which in several respects presents a remarkable similarity to that of 
Helix. here are well-developed multifid vesicles, and an elongated sac containing 
a singular organ in the form of a curved cylinder beset with numerous palmate spines, 
