424 UNITED STATES GEOLOGICAL SURVEY OP THE TERRITORIES. 



The nodes mentioned above are directed out at right angles to the sides 

 of the shell, and, like the costse, become again smaller toward the aperture. 

 Most of the large cosfie bifurcate at the nodes on the body-part of the shell, 

 but their number is also increased by the intercalation of others between. 

 Where they thus branch at the nodes on one side, the two divisions crossing 

 over the periphery from the point of bifurcation never both connect at a node 

 on the opposite side, but in most cases one, and sometimes each division, ter- 

 minates between two of the nodes on the other side. 



The septate portion of the only specimen of this species in the collec- 

 tion being highly crystalline, the structure of its septa cannot be very clearly 

 traced out. The siphonal lobe, however, can be seen to be a little longer 

 than wide, with a rather narrow body, provided with three branches on each 

 side, the upper pair of which are small and nearly simple ; while the. next 

 pair are longer and each bifid, and the terminal pair (which are larger than the 

 second) are each ornamented by three small pointed branchlets, or digita- 

 tions, on the outer side. The first lateral lobe is somewhat irregularly tripar- 

 tite ; the lateral divisions being bifid and sharply digitate, while the terminal, 

 which is not exactly central, is longer than the others, and has about five 

 pointed digitations, or sharp, nearly or quite simple, branchlets. The first 

 lateral sinus can be seen to be deeply divided at the extremity into two nearly 

 equal branches. The second lateral sinus can also be so far traced as to show 

 that it is not more than about one-third as large as the first, nearly as long as 

 wide, and regularly tripartite; and this is as far as the structure of the septa 

 can be made out from the specimen. 



Length, 2.10 inches; height, 1.76 inches; greatest convexity, measur- 

 ing to the extremities of the nodes on opposite sides, 1.25 inches; same 

 between the nodes, 1 inch. 



This species is somewhat related to S. hippocrepis, Dekay, sp. (= Am- 

 monites hippocrepis, Dekay, Ann. N. Y. Lyceum, Nat. Hist., II, pi. v, fig. 5), 

 but differs in having its body-part less extended, and in being higher in pro- 

 portion to its length. Its nodes are also larger and much more prominent; 

 but the most marked differences between these two forms are in their septa, 

 the siphonal lobe of the form under consideration being proportionally much 

 narrower, and provided with three, instead of only two, branches on each 

 side, while its first lateral lobe is tripartite (an unusual feature in the genus) 

 instead of bifid. It is also related to S. Texanus, Roemer (Kreid. von Texas, 



