

INVERTEBRATE PALAEONTOLOGY. 447 



forms properly belong to it. Yet, even authors who are fully aware of this 

 fact, still use it as a receptacle for Cretaceous species belonging to groups 

 that have not vet been separated under other names; that is, when they 

 either have not the necessary specimens, or do not desire to propose new 

 groups for the reception of species that they have to notice. 



A in in o ii i I e s co m i> leins, H. & M. 



Plate 24, tigs. 1, a, b, c. 



Ammonites complexus, Hall and Meek (18o4), Mem. Am. Acad. Arts and Soi. Boston, V (rj.s.), :!94, pi. iv, 

 fig. 1.— Gabb (1861), S.vnop. Moll. Cret. Formation, 9.— Meek (1SH4), Smithsonian 

 Check-List N. Am. Cret. Fossils. 24. 



Shell compressed-subglobose ; periphery broadly rounded; umbilicus 

 rather small and deep; volutions five or more, broader than high, inner ones 

 about half hidden within the dorsal groove of each succeeding turn, orna- 

 mented near the umbilicus by a row of small transversely-elongated nodes, 

 which, on the outer whorls of larger specimens, extend outward and bifurcate, 

 so as to form a series of rather distant, obscure costa?, which, with others 

 intercalated between, pass over the periphery ; surface, so far as known, 

 otherwise smooth, or only marked by obscure lines of growth. 



The largest specimen found (which wants the outer non-septate portion), 

 measures about 1.60 inches in its greatest diameter, by about 1 inch in con- 

 vexity. Adult examples must have been at least 2 inches broad, and may 

 have attained a considerably larger size. 



Septa crowded and complex ; siphonal lobe somewhat longer than wide, 

 with its body forming about one-third of its breadth, and bearing three 

 opposite, more or less divided, and digitate branches, the two terminal of which 

 are larger than the others, and show a tendency to bifurcate; first lateral 

 sinus as long and nearly as wide as the siphonal lobe, with a narrow, some- 

 what zigzag body, provided with one or two more or less digitate, alter- 

 nately-arranged, lateral branchlets, and two much larger, unequal, tripartite 

 and digitate terminal branches : first lateral lobe of the same length as the 

 siphonal, with a narrow body and three or four more or less deeply-divided 

 and variously digitate lateral branches, and a terminal trifid central branch; 

 second lateral sinus a little smaller than the first, but very similar to it in all 

 its details, excepting that its corresponding branches are on opposite sides; 

 second lateral lobe about three-fourths as long, and nearly as wide as the 

 first, which it nearly resembles in its branches, excepting that it has one 



