100 BULLETIN OF THE 



siphon composed wholly of coccal prolongations of the septa them- 

 selves.* The discovery of the adult corresponding to the young of 

 Endoceras is yet to be made, and even the young of Endoceras has, I 

 believe, never been described. A fragment of an Endoceras, the 

 Orthoceras duplex of Verneuil and Keyserling, can be even more 

 closely compared with the young of Nautilus, than our American 

 species. In this the septa bend posteriorly, forming extraordinarily 

 long funnels. Instead of simply connecting adjoining septa, as in the 

 ordinary forms, the funnel overlaps and extends just twice as far, to a 

 point opposite to the second younger septum, posterior to that from 

 which it takes its rise.f This compares with the tendency of Nautilus 

 to increase the length of the funnel in the young, and the slighter dis- 

 tinction which exists between the texture of the sheath and the siphonal 

 funnel itself, until at the earliest period, the siphonal ccecum is wholly 

 composed of the siphonal funnel closed at the posterior end. Evidently 

 a similar method of development is to be anticipated in Orthoceras 

 duplex, and as the funnels extend so far, we ought also to find more 

 than one ccecum. That is just as in the young Nautilus Pompilius we 

 find that the sheath of the second septum extends into the siphonal 

 coecum and is closed, forming really a second ccecum ; so, in the young 

 of 0. duplex the siphonal funnel of the second and third septa at least 

 will probably be found fitting into the siphonal ccecum, and closed at 

 the bottom. 



I have industriously examined the young of Orthoceras in order to 

 ascertain whether they too had any close resemblance to the adult of 

 Endoceras ; so far, however, my search has been fruitless, probably 

 owing to the unfitness of the forms which have come into my hands 

 for microscopical examinations. In the group of the Vaginati to which 

 Endoceras belongs, it is common to find the huge siphon filled to a 

 greater or less extent by calcareous deposits, differing considerably 

 from those filling the living chamber and the septal chambers. Bar- 

 rande, with his masterly grasp of facts, has demonstrated that these 

 deposits are made by a posterior prolongation of the body of the 

 visceral sac, and are not the result of fossilization. Barrande, also, con- 

 siders the cones of Endoceras to have been deposited in a similar 



* If, indeed, any septa remain in the extreme young. 



t De Verneuil and Comte de Keyserling, Russie et l'Oural. Vol. II, Plate XXIV, 

 Fig. 7. 



