DE80EIPTIONS OF SPECIES. 447 



ville reg^ion which was likewise identified as Pi. occidentalis for the Leadville mono- 

 graph." In general configuration it closelj^ resembles the specimen previously 

 described, but has the surface above the umboual ridge (if one wei'e present) crossed 

 by five or six delicate radial I'ibs, with two or three others of equal strength below. 

 Locality a/nd horizon. — San Juan region (station 2343); Rico formation. Lead- 

 ville district (station 227.5?); upper portion of the Weber formation. 



EDMONDIA de Koninck, 1844. 



Edmondia gibbosa Geinitz (non Astarte gibbosa McCoy). 



PI. IX, figs. 7, 8, 9. 



1866. Astarte (jihhasa. Geinitz, C'arb. uud Dyas in Nebraska, p. 16, tab. 1, figs. 'Z'A, 24. 

 Upper Coal Measures: In the gray limestone of Plattsmouth, Nebr. 



There are in the collection several specimens representing a form to which that 

 described by Geinitz as Astarfe g/Mosa McCoj', seems to be, among available litera- 

 ture, the nearest related. Characteristic specimens of this form are found in the 

 Rico formation at stations 2340 and 2341, and it seems to be represented by several 

 young examples at station 2342. The specimens collected at stations 2340 and 2342 

 are in the closest agreement, just as are those from the Hermosa formation at stations 

 2-2()4: and 2205 Avhich I have identified as J^. subtruncata. 



The Colorado material is in the form of internal casts, upon which a number of 

 low concentric folds are all that is left of the surface sculpture, but in shape, con- 

 vexity, etc., it agrees with some finely preserved specimens from Graham, Young- 

 County, Tex., which are referred with confidence to the same species. Here the 

 shell is seen to be ornamented with prominent lamellose concentric ridges, regularly 

 disposed at intervals, with more or less inconspicuous growth lines intervening. 

 The shell is rather tumid, suborbicular in shape, with the posterior outline slightly 

 flattened, giving it a subtruncato appearance. 



This species diflers from Edmoiidm siMruncata, which it resembles in a general 

 wa\' in shape and possibly in surface ornamentation. It is smaller, moi-e gibbous, 

 and longer in proportion to its width. 



The fossils from Colorado and Texas correspond closely to Geinitz's figures and 

 description, and probabl}' represent the same form with which he was dealing, but it 

 is doubtful if the latter was correctly referred by him to McCoy's species. 



This identification should not l)e confused with Edmondia gibhosa Swallow, which 

 is probably quite different. 



Locality and ho-rlzon. — San Juan region (stations 2340, 2341, 2342?); Rico 

 formation. 



au. S. Geol, Surv., Mou.. vol. 12, 1886, p. 70. 



