INVERTEBRATE PALAEONTOLOGY. 341 



Scalaria, it has to retain its original specific name cerithiformis. II" the name 

 Chemnitzia as here used should prove identical with Loxonema, however, 

 the name of this shell will, of course, have to be changed to Loxonema 

 cerithiformis. 



Locality and position. — Moreau Trading Post ; in the Fox Hills group 

 of the Upper Missouri Cretaceous series. It seems to be very rare. 



LITTORINIDyE. 

 Genus SPIRONEMA, Meek. 



Synon. — Turbo (sp.) aud Tuba (sp.) of authors (not Turbo, Linn., nor Tuba, Lea). 



Spironema, Meek (1864), Smithsonian Check-List N. Am. Cret. Fossils, 35.— Stoliczka (1868), 



Palreont. Indica, II, 263. 

 ? CaUouema, Conrad (1873), Appendix to Kerr's North Carolina Geological Report, V2. 



Eti/m.—c-elpa, wound around ; rf /f ia, a thread ; in allusion to the spiral lines of the type species. 

 Type. — Turbo ienuilineatvs, Meek and Hayden. 



Shell turbinate or subovate, thin; spire rather prominent; suture chan- 

 neled ; axis perforated ; aperture ovate, not modified by the body-volution 

 above; peristome continuous; outer lip sharp; inner lip thin, not reflexed or 

 flattened below, and only connected with the body-volution toward the upper 

 part of the aperture ; umbilical perforation small ; surface with revolving lines 

 and furrows. 



The shell for the reception of which this genus was proposed, has much 

 the form and general appearance of some of the Cretaceous species referred 

 by d'Orbigny and others to the genus Turbo. It differs, however, from that, 

 and indeed all other genera of the Turbinidce as properly restricted, in its 

 entirely non-pearlaceous interior, as well as in its distinctly-channeled suture. 

 In first referring it doubtfully to the genus Turbo, we had attributed its 

 want of the usual pearly luster to some change that the substance of the shell 

 had undergone while embedded in the rock. The fact, however, that the 

 associated Ammonites, Baculites, Margarita, Nucula, Inoceramus, and other 

 pearly shells, retain their nacreous luster, shows that this cannot be the case ; 

 and, from its combination of characters, there is little or no reason to doubt 

 that it belongs to the family Littorinidce. 



It differs, however, from the genus Littorina, in the greater thinness of 

 the whole shell, but particularly in its inner lip, which is neither reflexed 

 nor in the slightest degree flattened ; also, in its perforated axis and distinctly- 

 channeled suture. In some respects, it resembles the genus Fossar, Gray; 



