134 COLORADO FORMATION AND ITS INVERTEBRATE FAUNA, [bull. 106. 



Locality and position. — In the Pugnellus sandstone near Malachite 

 post-office, and in Poison canyon, Huerfano park, Colorado; at the 

 same or a somewhat lower horizon on the Arkansas river, 20 miles above 

 Pueblo, Colorado. 



NATICID^E. 



Genus LUNATIA Gray. 



Ltjnatia concinna Hall & Meek (sp.). 



PI. xxix, Figs. 9 and 10. 



Natica concinna Hall & Meek, 1856, Mem. Am. Acad. Arts and Sci., n. 8. vol. v, p. 384, 



PI. 3, Figs. 2a-d. 

 Natica moreauensis Meek & Hayden, 1856, Proc. Acad. Nat. Sci., Phila., p. 64. 

 Lunatia concinna Meek, 1876, U. S. Geol. Sur. Terr., vol. ix, p, 314, PI. 32, Figs, la-c) 



Whitfield, 1880, Geol. Bl. Hills of Dak., p. 430, PI. 12, Fig. 13. 

 Compare Natica obliquata Hall & Meek, 1856, op. cit., p. 384, PL 3, Figs. 1 a and b ; and 



N. rectilabrum Conrad, Jour. Acad. Nat. Sci., Phila., 2d ser., vol. iv, p. 344, PI. 58, 



Fig. 28. 



Prof. Meek's revised description is as follows : 



"Shell obliquely rhombic-subovate, or subglobose; spire moderate; 

 volutions three and a half to four, convex, and separated by a deep 

 suture, last one comparatively large,- surface marked by fine, rather 

 obscure, lines of growth, crossed by nearly obsolete, minutely flexuous, 

 revolving striae, only seen on well-preserved specimens; aperture sub- 

 ovate, being straighter on the inner than the outer side; umbilicus, 

 small and sometimes showing a slight tendency to develop a small 

 revolving ridge within; inner lip a little thickened and slightly reflected 

 upon the body volution above the umbilicus. 



" Length of a mature rather gibbous specimen, 0.90 inch; breadth 

 of same, 0.76 inch. 



"This shell varies somewhat in form, some individuals being pro- 

 portinally a little shorter, and having the body volution more ventri- 

 cose than others. For a long time it was believed to be distinct from 

 JV. concinna, and consequently the name N. moreauensis was proposed 

 for it. Since seeing a good series of specimens, however, showing the 

 form and general appearance of the shell at various stages of growth, 

 I am led to believe that it is not specifically distinct from the type of 

 N". concinna, which is now believed to be a young individual. At any 

 rate, small specimens before me of the same size seem to agree almost 

 exactly with the type of N. concinna, while I am at a loss to separate 

 these specifically from the larger individuals, such as those for which 

 the name N. moreauensis was proposed." 



The author then proceeds to compare this with the closely related 

 species Natica obliquata and JV". rectilabrum. According to Mr. Gabb 

 all the names given above, and N". acutispira Shumard, are synonyms 

 of Lunatia obliquata. This conclusion is quite probable, but I am unable 

 to confirm it with the material at hand. 



