DESCRIPTIONS OF SPECIES. 461 



This form has been found at two localities in the Rico formation, stations 23i5 

 and 234:2, at the latter of which it is fairly common. The Colorado specimens are 

 closely similar to Worthen's species and are probably identical. Loxonemaf peori- 

 ense is so different in the character of its surface ornamentation from at least our 

 American Carboniferous representatives of Loxonema as to suggest that its affinities 

 are elsewhere, possibly with Streptads Meek. 



Locality and horizon. — San Juan region (stations 2342, 2345); Rico formation. 



Loxonema sp. 



The onh' specimen representing this species is unfortunately very imperfect. 

 It seems to be a rare form, more nearly related to Loxonema halU Norwood and 

 Pratten than to any with which I am acquainted. 



Ijx-ality and horizon. — Leadville district (station 2275); upper portion of the 

 We))er formation. 



PLATYCERAS Conrad, 1840. 



Platyceras parvum Swallow. 



PL X, figs. 1, la, 2, 2a. ^ 



1858. Capulus 2]arviis. Swallow, Acad. Sci., St. Louis, Trans., vol. 1, p. 205. 



Coal Measures: Valley of the Verdigris, Kans. 

 1872. Platyceras nehrascensis. Meek, U. S. Geol. Surv. Nebraska, p. 227, pi. 4, figs. 15a, b. 



Upper Coal Pleasures: Three-fourths of a mile west of Nebraska City Landing, Nebr. 



Middle Coal Measures: Illinois. 

 1875. Platyceras nehrascense. White, U. S. Geog. Geol. Surv. AV. 100th Mer., Kept., vol. 4, p. 159, pi. 

 12, figs, oa-d ( Whole volume published in 1877. ) 



Carboniferous: Near Santa Fe, N. Mex. 

 1884. Platyceras nebrascene. White, Geol. Surv. Indiana, 13th Eept., p. 159, pi. 32, figs. 15, 16. 



Coal Measures: Eugene, Edwardsport, and New Harmony, Ind. 

 1890. Capulus pan-US. Key es. Am. Geol., vol. 6, p. 9. 

 1890. Capulus parvus. Keyes, Acad. Nat. Sci. Philadelphia, Proc, p. 177, pi. 2, figs. 14a-c. 



Upper Coal Measures: Indiana; Iowa; Nebraska; Kansas; and New Mexico. 

 1895. Capulus parvus. Keyes, Missouri Geol. Surv., vol. 5, p. 180, pi. 54, figs. 5a, b. (Date of imprint, 

 1894.) 



Upper Coal Mea,sures: Kansas City, Mo. 



Only two specimens in the collections were found representing this species, but 

 one of them is the lai-gest individual I have ever seen belonging to it. It measures 

 no less than 35 mm. across the base, and its longest diameter is 47 mm. 



Keyes places Platyceras nebraslcense Meek in the sj^nonymy of Capulus p>arvus 

 Swallow. Swallow's description seems to apply to Platyceras nehraskense, and the 

 figures given bv Keyes of a specimen supposed to be the type of PI. parvum cer- 

 tainly look as if the original might have been a young example of Meek's species. 

 On the other hand, we have the statement by Meek, ' ' This species resembles more or 



