INVERTEBRATE PALAEONTOLOGY. 419 



surface ornamented by small costa?, which pass from the inner side of the 

 volutions to about half way across their lateral surfaces, where they swell 

 into small, obscure, transversely-elongated nodes, and then branch each into 

 two or three smaller linear ribs, all of which pass straight over the periphery. 



Length, 0.87 inch ; height, 0.63 inch ; convexity, 0.33 inch. 



The septa of this species are comparatively rather simple, being each 

 provided with but two principal lateral lobes on each. side, none of which are 

 deeply divided. The siphonal lobe is longer than wide, and has two very 

 small, short, nearly parallel, obscurely bifid, terminal divisions, with a more 

 oblique, somewhat similar branch on each of the sides above. The first 

 lateral sinus is wider than the siphonal lobe, and nearly as long, with its 

 extremity deeply divided by a slender, obscurely trifid, auxiliary lobe, into 

 two very unequal, more or less sinuous, and obtusely digitate branches. 

 First lateral lobe about half as wide as the siphonal, but somewhat shorter, 

 and bearing two very small terminal divisions, similar to those of the 

 siphonal lobe. Second lateral sinus not larger than the outer division of the 

 first, and merely obscurely divided into two very short, simple, obtusely- 

 rounded, terminal subdivisions. Second lateral lobe very small, and obscurely 

 trifid at the end. Whether this last is what is usually called a ventral lobe, 

 or whether there is another still smaller one beyond it, the specimen is 

 scarcely in a condition to show. 



At one time, I was inclined to think a very small species described by 

 Dr. Shumard from the Cretaceous rocks of Texas, under the name Scaphites 

 vermiculus, might be identical with this ; but a sketch of that species sent to 

 me some years back by Dr. Shumard, shows it to be entirely distinct, being 

 even a more slender, differently-marked shell, with a proportionally much 

 larger umbilicus, and a longer deflected body-portion ; that is to say, it pre- 

 sents the characters of the distinct section Macroscaphites. 



This species is perhaps more nearly allied to S. Htigardianus, d'Orbigny 

 (Pal. Fr., I, Terr. Cret., 525), than to any other foreign form, but yet differs 

 too much to require a critical comparison, or detailed statement of differences. 



Locality and position. — Eastern base of the Black Hills ; from the Fort 

 Benton group, of the Upper Missouri Cretaceous series. 



