380 Systematic Paleontology 



" 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, 

 ornamented 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 costce, 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 por- 

 tion) measures about 1.6 in. in its greatest diameter by about 1 in. in con- 

 vexity. Adult examples must have been at least 2 in. 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 ter- 

 minal of which are larger than the others and show a tendency to bifur- 

 cate; first lateral sinus as long and nearly as wide as the siphonal lobe, 

 with a narrow, somewhat zigzag body, provided with one or two more or 

 less digitate, alternately 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 corre- 

 sponding 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 lateral branch less on each side ; 

 third lateral sinus shorter than the second and bearing about the same 

 relations to it in its branchings that the second lateral lobe does to the 

 first ; third lateral lobe about two-thirds as long and nearly as wide as the 

 second, with three subequal, spreading and digitate terminal branches; 

 fourth lateral sinus less than half as large as the third, oblique and usually 

 tripartite at the end, the branches being nearly simple. Beyond this there 



