349 Mr. Clark on some species ofAinialida. 



Naiitilt, (the Orlhocerata of Lamarck,) which strongly proves 

 that those shells cannot be internal ones; that is, the various 

 shapes of the same species. I have in my cabinet more tlian thirty- 

 specimens of Montagu's Nautilus Legumen, which he has figured 

 in Test. Brit, from a broken shell, and described as surrounded 

 by a rim or margin ; this is never the case except when some of 

 the anterior chambers are wanting ; then it has that appearance ; 

 but when perfect, the aperture gradually tapers to a striated ter- 

 mination. Montagu has also from the varieties of this shell formed 

 several distinct species ; for example, his Nautilus rectus is only 

 a straight and cylindrical variety ; and his A'", subarcualus is 

 another variety, having the three anterior chambers more globose 

 than the others. Of my thirty specimens, tliere are not two alike 

 in shape, some being straight, cyrnidrical, with the chambers 

 more or less inflated, and having an extremely sharp posterior 

 termination ; some being flat, arcuated, and obtuse ; and others so 

 distorted as to form right angles. 



Though nature varies in the outward forms of animals of the 

 same species, I believe that no particular internal part or bone 

 ever varies much, if at all, in form. The bone of the Sepia offici- 

 nalis^ or of the Loligo vulgaris, is always of an uniform shape. 

 From these circumstances it may be inferred that the Orthoceraia 

 cannot be internal shells, inasmuch as of the species O. Legumen, 

 scarcely two can be found alike. These facts appear to go far in 

 proving that most of the discoid and elongated polythalamous 

 shells called Nautili by the old writers, do not belong to the Ce- 

 2)halopo (la, hat are much more closely allied to the Annelida. The 

 very shape of the shells divided by septa into segments, coupled 

 with the facts above mentioned, sanction the idea that they are 

 inhabited by animals of the Annelida. 



The day before my departure from the sea side, I obtained 

 alive a fine specimen of the Turbo Clathratulus of Montagu, 

 which is a Scalaria in M. Lamarck's arrangement, belonging to 

 the division " Scalariens," and forms a part of his first section of 

 the Trachcl/podes, " sans siphon saillant," and which are gene- 

 rally Phytophagous. The animal I found to be Zoophagous, hav- 

 ing a distinct long retractile proboscis, with a very short siphon 



