INVERTEBRATE PALAEONTOLOGY, 425 



fal). 1. fig. 4), though its septa differ as widely from those of that species as 

 from those of S. hippocrepis. 



Locality and position — Chippewa Point, near Fort Benton, on the 

 Upper Missouri ; from the Fort Benton group of the Upper Missouri Creta- 

 ceous series. Specimen discovered by Lieut. John Mullen, of the United 

 States Topographical Engineers. 



Scaphites ventricosus, M. & H. 



Plato 0, tigs. 7, ii, b ; also, tigs. 8 and 8, a, b. 



Sayhiiix veatricosua, Meek and Hayden (186-2), Proceed. Acad. Nat, Sci. Philad.,XIV,22.— Meek (18G4), 

 Smithsonian Check-List N. Am. Cret. Fossils, - J4. 



Shell attaining a medium or larger size, oval, ventricose, broadly rounded 

 over the periphery ; inner turns closely involute, deeply embracing, and 

 composing a large portion of the entire bulk ; deflected portion very short ; 

 umbilicus very small and deep ; aperture transversely sublunate or reniform, 

 being deeply sinuous, and but slightly disconnected from the inner turns on 

 the inner side ; surface ornamented with costse that pass nearly straight over 

 the periphery, where they are of uniform size, excepting their gradual 

 enlargement with the volutions, while on the sides of the last or outer volu- 

 tion, about every fifth or sixth one is larger and more prominent than the 

 intermediate ones, which latter do not extend inward to the umbilical margin. 



The septa, as made out from the specimen represented by our figures 

 8, a, b, (which is believed to be the inner volutions of this species, as repre- 

 sented by figures 7, a, ft), are provided with deeply-divided lobes and sinuses. 

 Siphonal lobe longer than wide, and bearing on each side of its very slender 

 body three branches, the two terminal of which are slightly larger than the 

 succeeding lateral ones, and each unequally bifid and digitate ; first lateral sinus 

 as large as the siphonal lobe, very narrow at its base, and profoundly divided 

 at its extremity into two unequal branches, of which the one on the siphonal 

 side is larger than the other, and, like the latter, deeply bifid, with sinuous 

 and obtusely digitate margins; first lateral lobe as wide as the siphonal lobe, 

 but somewhat shorter, and provided with two nearly equal, bifurcating, and 

 digitate terminal branches; second lateral sinus not more than half as long, 

 and little more than half as wide as the first, and somewhat similarly divided 

 and subdivided ; second lateral lobe about half as long and wide as the first, 



but tripartite at the extremity, the divisions being nearly equal and digitate; 

 54 h 



