778 THE PALEONTOLOGY OF MINNESOTA. 



[.Canioroceras 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 E. 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 E. proteiforme* Furthermore, 

 the several varieties ascribed to E. proteiforme, such as vars. lineolatum, strangulatum, 

 tenuistriatum, are now known to have been founded upon incarcerated shells of 

 Orthocer<ts and Clinoceras. 



It may, in a general way, be said that Endoceras 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 XLVII, 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 a smaller 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 XLJX, figure 2, where, at the 



These statements have no bearing 'upon the remarkable species K. longiHxiimiHi and /-'. iiinltittiliHliittim of tin: Blai-K 

 Itivi-r limestone, In which the successive Invuglnated sheaths are part of the siphon. Such shells are representatives of 

 the'genus VaginoCcrat, Hyatt. 



