778 THE PALEONTOLOGY OF MINNESOTA. 
[Cameroceras proteiforme. 
light of our increased knowledge, at once correct themselves. The composition of 
the entire sipho was not then fully understood. We have already adverted to the 
fact that it consists of a continuous and to some extent solid apical cone followed 
above through all the mature and later chambers of the shell by a discontinuous 
tube composed only of the deflected septal funnels. The continuous parts of such 
siphones were originally regarded and designated as “embryo-tubes” or “shells,”’ 
and, as an easy inference, all apparently similar internal tubes were thus interpreted. 
We now refer to the shell of Cameroceras only the internal tube formed by the 
consolidation of the sipho and its few subsidiary sheaths. All other tubes are 
adventitious, hermit orthocerans or cyrtocerans of various species, which, as we have 
already observed, found favorite retreats in the great siphones of these dead shells. 
Such occurrences are extremely frequent, and the finding of as many as four or five 
such tramp shells ensconced side by side in a siphonal cavity is not unusual. Hence 
we are compelled to look upon such species as Endoceras duplicatum of the Trenton 
limestone of Middleville, N. Y. and EL. gemelliparum of the Black River limestone of 
Jefferson county, N. Y., as based upon unessential and adventitious characters, and 
the latter as probably a portion of the mature shell of L. proteiforme.* Furthermore, 
the several varieties ascribed to EL. proteiforme, such as vars. lineolatum, strangulatum, 
tenuistriatum, are now known to have been founded upon incarcerated shells of 
Orthoceras and Clinoceras. 
It may, in a general way, be said that Hndoceras proteiforme is characterized by 
its enormous size, circular section, comparatively shallow air-chambers and great 
submarginal sipho. The size attained by the species is best indicated by the large 
cast of the siphon as shown on plate xivu, and entire shells referable to this species 
have been found with a length of ten to fifteen feet, though all the material before 
me is of asmaller size. The difference in the aspect of these fossils at different 
parts of their length, where the siphonal tube is variously constructed and the septa 
subject to variations in distance, renders most appropriate the specific name 
proteiforme. 
One of the characters. which is very helpful in distinguishing the siphonal casts 
of this from associated but rarer species of the genus, is the shortness of the siphonal 
funnels. The air-chambers are themselves shallow, but the funnels seem at times 
not even to extend from one to the next. The distance between the septa and 
consequently the length of the siphonal funnels increases toward the body-chamber, 
but this variation is rarely so abrupt as shown in plate xtrx, figure 2, where, at the 
* These statements have no bearing upon the remarkable species E. longissimum and E. multitubulatum of the Black 
River limestone, in which the successive invaginated sheaths are part of the siphon. Such shells are representatives of 
the'genus Vaginoceras, Hyatt. 
