CEPHALOPODA. 16 



In Others, the Orthoceratites*, it is altogether straight. It is 

 not improbable that the animals belonging? to these shells, resem- 

 bled that of Nautilus or of the Sjjirula. The 



Belemnites 



Probably belong also to this family, but it is impossible to ascertain 

 the fact, as they are only found among fossils ; every thing, however, 

 proves them to have been internal shells ; thin and double, that is, 

 composed of two cones united at the base, the inner one much shorter 

 than the other, and divided into chimbers by parallel septa, which are 

 concave on the side next to the base. A siphon extends from the 

 summit of the external cone to that of the internal one, and continues 

 thence, sometimes along the margin of the septa and sometimes 

 through their centre. The interval between tlie two testaceous cones 

 is filled with a solid substance, in some composed of radiating fibres, 

 and in others, of self-involving conical layers, the base of each being 

 on the margin of one of the septa of the inner cone. Sometimes we 

 only find this solid portion, and at another we also find the nuclei of 

 the cliainbers of the inner cone, or what are termed tlic honeycomb 

 cells. Most commonly these nuclei and the chambers themselves 

 have left no other traces than some projecting circles on the inside of 

 the internal cone. In other specimens again we find more or fewer 

 of the nuclei, and still in piles, but detached from the double conical 

 sheath that enveloped tliem. 



Of all fossils the Belemnites are the most abundant, particularly in 

 chalk and compact limestone. f 



M. de Blainville divides them according to the greater or less depth 

 to which the internal cone or chambered portion penetrates, or as the 

 edges of the external cone have a small fissure or not, or as the exter- 

 nal surface is marked on one side by a longitudinal furrow, or by two 

 or more furrows towards the summit, or finally as that surface is 

 smooth and without furrows. 



Bodies very similar to Belemnites, but without a cavity and with 

 a rather prominent base, form the genus actinocamax of Miller. (a) It 



* Breyn. de Polythal., pi. iii, iv, v, and \\. ; and Walch, Petiif. of Knorr., Supp. 

 IV, 1), iv, d, iv. See also Sage, Joum. de Phys. an. IX, pi. 1, under the name of 

 Belemnite. 



t The best works on this singular genus of Fossils, are the Memoires sur les 

 Beletnnifes considerhs zoologiquement el geologiquement, by M. de Blainville, Paris, 



{j:^ {aj ^Ir- Miller gives the following description of the genus Actinocamax 

 which he has established and separated from the Belemnites. 



Gen. Char. A club-shaped Spathose concretion, consisting of two nearly equal, 

 longitudinal adhering portions. Apex pointed : base a convex, but obtuse cone. 

 The whole formedof a series of enveloping fibrous laminse. 



Specific character. Act. verus. A club-shaped Spathose semi-transparent horn 

 coloured concretion ; base convex, obtuse, conical ; apex submamillar. Sides de- 

 pressed towards the lower end, showing two longitudinal, towards the apex branch- 

 ing, impressions of blood vessels. 



The species was found in the Chalk Strata in Kent, Wiltshire, and Sussex, in the 

 strata which contain marine animals, so that Mr. Miller does not hesitate to consider 

 it as an inhabitant of the sea. — ExG. Ed. 



