39 



each side, after which they bifurcate widely, but very indistinctly, before 

 passing over the periphery. In the earliest part of the whorl, two simple, 

 secondary ribs, which do not quite reach to the sutures, usually inter- 

 vene between each pair of pi'imaries. Near the aperture the secondary 

 costoe disappear, and the ribs as they pass over the siphonal edge become 

 much more distant. As viewed along the pei"iphery, the whole of the ribs 

 are about equidistant, the intermediate ones being as broad and as wide 

 apart as the bifurcations of the primaries. The entire costation is pecu- 

 liar in another way ; the ribs, though wide, are obtuse and not much 

 elevated, and the corresponding depressions, though broad, are always 

 very shallow. At some distance fi'om the aperture, where the test is 

 preserved, both ribs and grooves are obtusely angular. Near the outer 

 edge of the volution they become more obsolete as well as wider, and 

 probably with age disappear altogether. 



Septation unknown. 



Greatest diameter of the shell, live iuche>^ and ten lines ; maximum 

 width of umbilicus, (from suture to suture) two inches and five lines. 

 Height of aperture, one inch and three and a half lines ; greatest breadth 

 of do., twentj'-three lines. 



The above description refers exclusively to the solitary and imperfect 

 specimen collected by Mr. Eichardson, which is represented at Plate VI. 

 Although only partially characterized at present, the sjaecies seem to 

 possess sufiiciently distinctive features to entitle it to the new name 

 which is here proposed for it. The sculpture of A. Carlottensis is not 

 very dissimilar to that of A. (Perisphinctes) tyrannus, but the shape of 

 the two shells is quite difterent. In A. Carlottensis the umbilicus is 

 comparatively small, in A. tyrannus it is very wide. In the former, 

 when undistorted, the inner whorls together would probably occupy 

 about one-third of the entire diameter; in the latter they would make up 

 more than half A. Skidegatensis resembles A. tyrannus in shape but not 

 in sculpture, while A. Carlottensis is allied to A. tyrannus in sculptui-e but 

 not in shape. 



Ammonites Laperousianus. (N. Sp.) 



Plate III., figure 3. 



Shell composed of many rounded but slightly compressed whorls ; 

 .umbilicus about one-half of the entire diameter; surface marked by 

 simple, transverse ribs, and by numei-ous, oblique, periodic constrictions 



