434 UNITED STATES GEOLOGICAL SURVEY OE TOE TERRITORIES. 



of the siphonal lobe,- which is oblong ia form, being about one-fourth longer 

 than wide, and provided with three unequal branches on each side, the two 

 terminal of which are nearly parallel, bifid, and digitate, and the laterals 

 smaller and merely digitate, or in part nearly simple ; first lateral sinus as 

 long as the siphonal lobe, but wider, and divided at the end into two very 

 unequal terminal branches, of which that on the siphonal side is much 

 broader than the other, and like it provided with three or four slender, 

 obtusely dentate branches ; first lateral lobe about the size of the siphonal, 

 or a little longer, and provided with two branches on each side, the two ter- 

 minal of which are spreading and unequal, that on the siphonal side being 

 shorter than the other and merely bifid and digitate, while the other is tri- 

 partite and digitate, its terminal branch being long; second lateral sinus con- 

 siderably smaller than the first, with a narrow body bearing two small, bifid, 

 terminal branches, and one or two short, unequal, alternating lateral divisions, 

 one of which, on the siphonal side, is broad and obscurely trilobate at the end ; 

 second lateral lobe a little more than half as long and wide as the first, with 

 two short, nearly equal, obtusely dentate terminal branches, of which the one 

 on the siphonal side shows a tendency to bifurcate; third lateral sinus hardly 

 more than half as large as the second, with merely two or three short ter- 

 minal, partly-lobed divisions; third lateral lobe only about as large as one of 

 the terminal divisions of the second, nearly oblong in form, and showing a 

 slight tendency to trilobation at the end; fourth lateral sinus smaller than 

 the third, and provided with two short, spreading, terminal branches, with 

 trilobate and bilobate ends; fourth lateral lobe somewhat larger than the 

 third, and rather deeply divided into two short, spreading, bilobate, terminal 

 branches. 



Length, 2.91 inches; height, 2.51 inches; convexity, 0.95 inch. 



This form holds almost an exactly intermediate position, as it were, 

 between the typical S. Conradi and S. Nicolletii, Morton {■=. S. comprimu, 

 Owen), both in external and internal characters. Externally, it differs from 

 the first in being more compressed, and in having its lateral tubercles almost 

 entirely confined to the inner volutions and the inner half of the outer one. 

 Its septa also conform very closely to those of the typical 8. Conradi, except- 

 ing that their divisions are proportionally shorter, less sharply digitate, and 

 their third lateral lobe much smaller and less deeply divided. 



I have described this form in more detail than is usually necessary for a 



