NATURAL SCIENCES OP PHILADELPHIA. 317 



This character, however, is not always so distinctly marked near the smaller 

 extremity, as along the larger half of the shell, where it imparts to the trans- 

 verse section a trigonal outline. In the form of its septa lobes, it is more 

 nearly related to B. compressus of Say, than to B. ovalus of that author, though 

 its form alone will readily distinguish it from either of these species. 



At the time I published the paper on some Cretaceous fossils from Vancouver 

 Island, cited at the head of this description, only a few fragments of this species 

 were in the collection examined. Thinking the flattening of the ventral side of 

 these probably due to accidental pressure, I referred them provisionally to B. 

 ovatus of Say. At the same time, however, I suspected they might belong to a 

 distinct species, and suggested for it, in case farther comparisons should prove 

 it to be new, the name B. occidentalism which is here adopted. 



Locality. Komooks, eistern shore Vancouver Island. 



Ammonites complexes var. Suciaensis. Ammonites complexus, Hall & Meek, 

 1856, Mem. Am. Acad. Arts and Sei. vol. 5, new ser. pi. 4, fig. 1, a. b. 



This shell agrees almost exactly in form with A. complexus, excepting that it 

 is more compressed, its volutions being distinctly narrower transversely, in pro- 

 portion to their diameter from the dorsal to the ventral side, than in that 

 species. In its septa, it agrees very closely also with A. complexus, the differ- 

 ences observable being apparently such ns may be due to the larger sizes of the 

 specimens of the form under consideration. 



The largest specimen in the collection is from Sucia Island. It is an internal 

 cast, and so much worn as to obliterate much of the details of the lobes and 

 saddles. It consists entirely of septate whorls, the outer non-septate portion 

 having been broken away. In its greatest diameter, it measures 4-60 inches, 

 and 190 inches in breadth or thickness. 



It is possible this shell may prove to be specifically distinct from A. complexus, 

 . but with my present means of comparison I do not feel fully warranted in 

 separating it. 



In the number, arrangement, and mode of branching of its septa lobes, as 

 seen in some of the smaller sized specimens from Komooks, it is also very 

 closely allied to A. Golkvillensis, of D'Orbigny ( = ^4. Lewisiensis, D'Orb. 

 Pal. Fr. tome 1. Cret. pi. 101, non Sowerby) ; though it is a more ventrico3e 

 shell, and wants the dorsal groove so characteristic of that species. Its cos se 

 also differ in being more strongly defined on the inner half of the whorls. 



Locality and position. Sucia Island, and at Komooks on Vancouver Island. 



Ammonites Vaxcouverensis. Shell discoid ; volutions increasing rather 

 gradually in size, strongly compressed on the sides, and flattened ou the narrow 

 dorsum, nearly twice as broad from the dorsal to the ventral side, as the 

 transverse diameter, rather deeply embracing; umbilicus of moderate depth, 

 about half as wide as the greater diameter of the outer whorl ; aperture (as 

 inferred from a section of the outer whorl) compressed cordate. Surface 

 ornamented by a row of compressed nodes along each dorso-lateral margin, 

 and another of smaller size around each umbilicus ; about twenty of the first, 

 and ten of the latter, may be counted on each side of an entire turn. 



The flattened sides between the dorsal and ventral rows of nodes, are pro- 

 vided with obscure, slightly arching, transverse cosrse, one of which extends 

 from each of the umbilical nodes towards the dorsal margin, but all become 

 obsolete before reaching it. Between each two of these principal costse, one or 

 two more very obscure ones are seen, which do not reach either the dorsal or 

 ventral margins. 



The specimen from which the foregoing description was made out, consists 

 of about the half of one volution, most of which is uon-septate. When entire, 

 the shell must have measured about 3-85 inches in its greatest diameter, and 

 near 1-13 in breadth at the aperture. It seems to be closely allied to A. 

 Leopoldianus, of D'Orbigny (Pal. Fr. Ter. Cret. t. 1, pi. 22, 23) but differs from 



1861.] 



