PLATE 53. 
1. 281. 13. Endoceras magniventrum. (Pag- 218.) 
1 a. A fragment, showing several of the chambers, with the large siphuncle projecting above. 
1 b. An artificial longitudinal section, showing the proportional diameter of the siphuncle and shell, as well 
as the extreme convexity of the septa, which are correctly represented as somewhat irregular in this 
respect. 
1 c. A transverse section of the larger extremity, which is worn off obliquely. At d d the outer line indicates 
the edge of the siphuncle ; the inner one being perhaps an exfoliation from the same, but too obscure 
to determine its character. At e, the embryo tube, with a young shell, is clearly distinguishable within 
the siphuncle. The position of the same is shown in the longitudinal section, which slightly cuts its 
outer edge. 
2. Endoceras proteiforme. (Pag. 213.) 
A large fragment of this species, in which the embryo tube is preserved, while the surrounding shell has been 
partially removed. 
