PLATE 50. 



Fig. 1, 2, 3. Endoceras proteifoeme. (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 6. 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 e, 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 escentric position of the siphuncle. 



3. An embryo tube, more conical than any of the others. 



