PLATE 15. 
1. 89. 1. Ormoceras tenuifilum. (Pag. 55.) 
1. A fragment of this species, partially covered with the delicate thin outer shell, presenting in the lower 
part of the figure some obscure markings of the septa; and above, showing the moderate convexity of 
a septum. 
i a. Transverse section of the same specimen, broken through the annulations of the siphon. 
16. A portion of the outer shell magnified, showing the fine undulating threadlike lines upon the surface. 
1 c. A longitudinal section of a portion of a large individual, showing the septa, which are composed of double 
plates reaching only to the inner lamina of the exterior shell. The distance between the lamina! is 
unusually great in the upper part of this specimen, the spaces between them being nearly as great as 
between the septa. 
