IIEEKMANTOWN AND CHAZY FORMATIONS OF CHAjNIPLAIN BASIN 42 1 



more central in position. There is hence little doubt that this species 

 is also a member of the Endoceratidae and probably referable to 

 Endoceras. Since we have not been able to establish whether the 

 funnels extend only to the preceding septum or to the second next 

 in apical direction, a conclusive reference has been impossible. 

 Neither have we observed any " darts " or endosiphocones indicat- 

 ing the formation of endosiphosheaths within the wide siphuncle. 

 Yet the solid character of the apical siphuncle would serve to indi- 

 cate that such a formation may have taken place there, though it was 

 still in an inceptive stage and did not extend very far, the greater 

 portion of the siphuncle being still used throughout lifetime as a 

 siphuncular chamber. 



E. consuetum Sardeson, from the Shakopee formation near 

 Pickett's Station Wis., is very closely related to this species. It 

 possesses the same rate of growth, depth of septa and relative width 

 of siphuncle, differing only in having the septa more closely arranged 

 by about one fourth. The obliquity of the sutures in the type of the 

 western form is largely or entirely caused by compression and some- 

 what exaggerated in the original drawing; it can not be held to 

 constitute a specific difference. 



Endoceras (?) hudsoni sp. nov. 



Plate 7, figure i 



The following description is based on a single specimen which, 

 however, well exhibits the principal diagnostic characters of this 

 type of cephalopods. 



Description. Large, very slightly curved, gradually expanding 

 cyrtoceracone. The length of the specimen is 22 cm; its minor (not 

 complete) width 65 mm; the major 104 mm. The curvature of the 

 conch is very slight^ (the hight of the inner arc 5 mm), though 

 apparently not accidental. The rate of growth is 20 mm in 100 mm. 



The living chamber has not been observed. The cameras are 

 relatively deep, the septa being 10 mm distant in the specimen ; the 

 septa are moderately concave, their depth equal to that of three 

 cameras. The sutures have not been observed. 



The siphuncle is of excessive size, its major diameter at the upper 

 end being 55 mm, its minor 43 mm ; so that it appears to have 

 occupied one half of the interior space of the shell. Its position is 



^ It is probable that the actual curvature would be found to be some- 

 what larger if measured along the siphuncular side, which in this specimen 

 is, on account of weathering, unsuited for this measurement. The section 

 [see text fig. 6] apparently elHptic, is not very well established. 



