ORTFIOCKUATIDE. 
71 
Fig. 7. 
Orthoccras angidatum^. — a, section showing sipliuncle with organic deposits 
(depots organiqnes) at the necks of the septa, which form obstruction- 
rings (anneaux obstructeurs) in the lower half of the specimen : natural 
size ; b, section showing sipliuncle, natural size ; <?, surface of test, of the 
natural size ; d, from a plaster cast of the surface of a larger specimen than 
c, showing a greater number of intermediate longitudinal riblets ; e, figure 
of a very fine specimen, half tlie natural size, part of the test is preserved 
upon the inner curvature of the shell ; f, section showing submarginal 
sipliuncle, natural size (cf. position of siphuncle in fig. h). 
^ Figures c and d are engraved from Swedish specimens kindly supplied to 
the writer by Dr. Lindstrdm, and now in the National Collection. 
