44 



Concluding Observations. 



In consequence of this distinction of sexes, the completion of the anatomy 

 of this interesting species awaits the arrival of a male specimen ; and not only 

 with respect to the generative system is further opportunity of dissection re- 

 quii'ed, but it is desirable for the perfect elucidation of the structure of all the 

 other organs ; for the anatomy of a species can rarely be satisfactorily founded 

 on the examination of a single individual, especially if it presents a new and un- 

 common form. Even with the greatest care, parts are liable to be displaced 

 before their relations to the surrounding structures have been sufficiently ascer- 

 tained; and it is only after having acquired such knowledge, that the better mode 

 of conducting the examination is perceived. But besides the Umited materials 

 which have been afforded for this inquiry into the structure of the Pearly Nau- 

 tilus, it is further to be regretted that so httle information should exist relative 

 to its habits and modes of action ; its defective histoiy in these particulars 

 having rendered it very seldom practicable to connect the modifications of the 

 different organs, when ascertained, with the peculiar exigencies of the species. 

 These modifications have, however, been carefully studied with respect to the 

 organization of allied groups of MoUusca, and some of the affinities of Nautilus 

 have thus been attempted to be demonstrated ; but many more doubtless remain 

 to be detected by the experienced naturahst. 



Before, however, entering on this subject, it is necessary to add a few ob- 

 servations on the relative position of the soft parts of Nautilus Pompilius to 

 their testaceous covering. The shell of this species, as is well known, is a sub- 

 orbicular, symmetrical, multilocular univalve, convoluted on a vertical plane, 

 with the turns contiguous ; the last being the largest, and concealing all the 

 rest ; the umbihcus being further obhterated by a deposition of nakrous matter*. 

 It is a thick and heavy shell, when compared with Argonauta, has a smooth 

 exterior, transversely marked with reddish brown bands, and is composed of 



* In another recent species {Nautilus vmbilicatus, Lam.), which much resembles the preceding in 

 form, colour, and size, the umbilicus is not obliterated, and the gjTations consequently are distinctly 

 visible from without. From the small fragment of shell remaining attached to the animal here de- 

 scribed, it was not evident to which of these species it had appertained : I therefore submitted both 

 of them to Mr. Bennett's inspection, who immediately selected Xautilus Pompilius as the shell to 

 which his specimen was attached when brought on board. 



