INVERTEBRATE PALAEONTOLOGY. 281 



a shell to go into Solidula, and almost certainly has not two folds on the 

 columella. 



Locality mid position. — Crow Creek, near the Black Hills, Dakota; 

 from the Fort Pierre group of the Upper Missouri Cretaceous series. 



v <■ i ; r o ii attenuatiis, M. & H. 

 Plate 19, fig. 17, a, b. 



.IrM on (Solidulal) altenuatus, Meek and Hayden (1858), Proceed. Acad. Nat. Sci. Philad., X, 54 

 Solidula attenuata, Meek and Hayden (1860), ib., XII, 185 ; and >'6.,424. — Meek, Smithsonian Check-List 

 N. Am. Cret. Fossils, 17. 



Shell elongate-subovate, approaching subterete, very thin; spire pro- 

 duced to about two-thirds the length of the body-volution ; whorls about 

 five, compressed-convex, last one narrow or subcylindrical ; suture distinct; 

 surface polished, and ornamented by small punctate revolving strife, generally 

 less than the spaces between on the spire, but more closely arranged and 

 less regular on the body-volution, near the base of which they become 

 stronger; aperture narrow, being very acutely angular above, widest below 

 the middle, and very narrowly rounded or subangular at the base. 



Length, 0.54 inch; breadth, 0.19 inch; angle of spire, near 22°. 



This species differs from the last remarkably in the relative, sizes of its 

 spire and body-volution; the former being proportionally much longer and the 

 latter much narrower than in the preceding species. The only specimen yet 

 found has the lip and the lower part of the columella broken away, so as to 

 leave room for doubts whether or not it had the characteristic fold on the 

 columella of Actceon, though I think I can see obscure evidences, on very 

 critical examination, of a single fold. If it has no fold, however, of course 

 it will have to be removed to the genus Actcsonina. 



I am not acquainted at present with any very nearly allied species. 

 In the Proceedings of the Academy of Natural Sciences of Philadelphia for 

 March, 1860, Mr. Gabb has figured a somewhat similar shell, from the Cre- 

 taceous rocks of New Jersey, under the name Actieonina biplicata, a name 

 that he attributes to Meek and Hayden; but I do not remember that we ever 

 described any such shell under that name. Mr. Gabb states that it has two 

 plications on the columella, and that he had supposed it to be new until he 

 saw our type-specimen at Washington, which he says is not in a condition to 

 show the folds on the columella, so clearly seen on the New Jersey specimen. 

 From his remarks, I think he must have seen the type of the species here 

 under consideration, and by some accident obtained a wrong name for it. 

 36 H 



