3G7 



known, however, it differs in the details of its septa, while in the pecu- 

 liar flattening of its dorsal or antisiphonal side it differs not only from 

 the last but from any other species of the genus known to me. I noticed 

 this peculiarity in the specimen first referred provisionally to Say's B. 

 ovatus, but supposed it due to some accident. The collections subse- 

 quently obtained, however, show that it is not due to accidental pres- 

 sure. It must be remembered, however, that individuals of the same 

 species in this genus are subject to some variations of form as well as of 

 the details of the septa ; while they often present so few characters 

 upon which to found species that their proper classification is generally 

 very difficult, excepting to those who would refer all such forms through- 

 out the world to the single species B. anceps of Europe. This form 

 bears somewhat the same relations to the last that jB. compressus, Say, 

 bears to his B. ovatus, its septa being very like those of the former ; so 

 far as known, however, it seems never to be so compressed as B. com- 

 pressus at any stage of growth.* 

 Locality and position. — Same as last. 



Genus HETEROCERAS, d'Orbigny. 



Heteroceras Cooperi, Gabb (sp). 



Plate 3, figs. 7 and 7 a. 

 Ammonites f Cooperi, Gabb (1S64), California Geol. Report, i, 69, pi. 14, figs. 23 and 23 a. 



Of this fossil, there is in the collection but a single non- septate frag ' 

 ment, measuring3.50 inches in length and about 1.90 inches in its greatest 

 breadth ; the section being slightly oval. It is evidently a part of a 

 spiral shell, with rounded disconnected whorls; and, judging from its 

 curve, it must have possessed a much larger umbilical space than is 

 seen in Turrelites. As it is very much larger than any known Selicoceras, 

 it would seem to have belonged to the non-septate part of a shell allied 

 to Heteroceras. Its surface is ornamented by moderately distinct annu- 

 lar costre, which pass around rather obliquely. Two rows of nodes 

 also occur on the outer or dorsal side, at which points the costas usually 

 bifurcate. 



I refer this shell with much doubt to the species described by Mr. 

 Gabb under the name Ammonites f Cooperi, which it seems probable 

 was founded on a fragment of a Heteroceras. Mr. Gabb referred his 

 species doubtfully to the genus Ammonites, as he had only mere frag- 

 ments for study. 



Locality and position. — Komooks, Vancouver's Island : Cretaceous. 



Genus AMMONITES, Bniguiere.f 

 ArsiMONTTES Newberrya]!^us, Meek. 



Plate 4, figs. 3, 3 a, and 3 I. 



Ammomtes Xiwitrriianus, Meek (1S57), Trans. Albany Institute, iv, 47 (not A. Xnc- 

 berryanus, Gabb. (1664), Geol. Report California, i, 61, pi. 27). 



Shell discoid, moderately compressed, rounded on the periphery; 

 umbilicus of moderate depth, less than one-third the greater diameter 



*Since this was ■written I have ascertained that Jarc/e specimens of B. compressus 

 show a tendency to present a similar subtrigonal section (see Invert. PaliPont. Upper 

 Mo., 403), from which it wonld appear that this Vanconver form may be more nearly 

 related to B. compressus than has been suspected. 



t None of the species here described belong properly to the genus Ammoniies, ae re- 

 stricted by late InTestig^tors of the family AMmonltida: As the Cretaceous groups of 



