THE TJlh^NTON LIMESTONE OP MANITOBA. 89 



PLATE VI. 

 Endoceras cRASSisiriioxATiM. (Page 7'.).) 



Fig. 1. — Oudine of tbo longest and most perfect sipliuncle collected, one-fourth the natural size. 



2. — Longitudinal section of a portion of another sipliuncle, shewing the gradual and irregular widening of the 



endosiphon anteriorly. 

 3. — Longitudinal section of a portion of a siphnncle, showing the narrow posterior part of the endosiphon, 



with, apparently, a few distant transverse dissepiments. 

 4. — Longitudinal section of the thickest portion of a siphnncle of Ihis species known to the writer, shewing the 



widening outward of the endosiphon anieriorly- At its narrower end the endosiphon is nearly filled 



witli an adventitious fragment ot an Orthoceratite. 



PLATE VIL 



Endoceras CRASsisirnoNATUM. (Page 79.) 



Fig. L — Exterior of the specimen represented on Plate VI, tig. 4. The upper part of the figure is an outline of a 

 transverse section at S, shewing the proportionate size of the endosiphon anteriorly. 



Ortiiocekas SiMi'.soNi. (Page 79.) 



Fig. 2. — Reproduction, in outline only, of Mr. Billings' original figure of the type of this species. 



o. — Portion of a sipliuncle, supposed to be referable to this species, from Dog's Head, Lake Winnipeg, to shew 



the obliquity of the septal annulations. 

 3a. — Outline of transverse section of the same, at S. 



PLATE VIII. 



Ortiioceras SiMrsoNi. (Page 80.) 



Fig. 1. — Natural and longitmliiial section of a portion of a cast of tlie interior of a shell whicli is supposed to belong 

 to this specie.?, shewing some of the septa and the lateral margins next to the test. Rather loss than 

 one-half of the specimen has been worn down, and the dotted lines indicate the outline of the siphnncle 

 as it would have appeared if the section had been through the middle of both shell and siphnncle. 

 la. — Outline of transverse section of siphnncle of the same at S, to shew the proportionate sizo of the 

 endosiphon. 



Orthoceras Selkirkhnse. (Page 82.) 



Fig. 2.— Lateral view of the most perfect specimen in the Survey collection, sliewing the shape and surface mark- 

 ings of the species. 

 2a.— Longitudinal section of a part of the same, to shew the characters of the siphuncle and septa. 

 2b.— Outline of transverse section of the original of fig. 2, at S. 



Ortiioceras SEjrirLANATUM. (Page 8L) 



Fig. 3.— Dorsal aspect of the only specimen in the Survey collection. 



oa.— Outline of transverse section of the same specimen, at S, to shew the sizo and relative position of the 

 siphnncle- 



Orthoceras Winnipkgbnse. (Page 82.) 



Fig. 4.— Lateral view of the most perfect sijecimen known to the writer. 

 4a. — Outline of transverse section of the same, at S. 

 4b.— Longitudinal section through the septate portion of the same. 



Sec. IV, 1891. 12. 



