PLATE 50. 
Fig. 1 , 2, 3. Endoceras proteiforme. (Pag. 213.) 
1 a. An embryo tube containing a young shell. This specimen is more elongated, and less rapidly attenuating 
than the prevailing forms of the species : the outer tube is smooth, while the inner one is striated. 
1 b. This tube is more slender than the usual forms, but does not differ in other respects. 
2 a , b. Fragments of smooth embryo tubes, apparently of the same species, differing only in being more 
suddenly contracted and aculeate near the apex. 
2 c, d. Parts of the siphuncle separated from larger shells, still retaining the embryo tube within. The si- 
phuncle is marked by oblique or ascending annulations, indicating the junction of the septa; which 
direction of the annulations is due to the lateral or excentric position of the siphuncle. 
3. An embryo tube, more conical than any of the others. 
