Logan.] The Invertebrates, Benton Group. 443 



Description of the Fort Benton Species. 

 CCELENTERATA. 



A fragment of coral, taken from the Lincoln marble a few 

 miles north of Lincoln Center, in Lincoln county, by Mr. Sahl- 

 man, of the latter place, probably belongs to the Stylophonidse 

 family of the Hexacoralla subclass. The specimen in my pos- 

 session is not sufficiently well preserved to present generic, much 

 less specific, determinative characteristics. In general appear- 

 ance the coral resembles the Devonian species Acervularia 

 davidsonii, but does not present the same regularity of coralla 

 structure. As tto species belonging to this subkingdom have 

 as yet been described from the Fort Benton formation, the find- 

 ing of such a specimen is important. Further search in this 

 horizon will probably result in the discovery of more perfect 



specimens. 



ECHINODERMATA. 



A single fragment of a crinoid stem was discovered among 

 Fort Benton rocks on the Cross ranch, in Mitchell county, by 

 Mr. O. S. Sommers, of Buel, Kan. The crinoid probably be- 

 longs to the family Encrinidse, but generic characteristics are 

 not clear. As a careful search of the locality in which this 

 specimen was discovered failed to disclose further specimens, its 

 occurrence in this horizon may be purely accidental. The sub- 

 stance of the crinoid resembles that of the Lincoln marble, but 

 if crinoids are to be found in this horizon, they are not abun- 

 dant. 



VERMES. 



Serpula plana, n. sp. PJate cxix, fig. 2. 



Cylindrical tubes growing in groups on the outer surface of 

 the large Inocerami of the Ostrea shales ; irregularly curved, 

 gradually increasing in size, neither regularly coiled nor 

 curved, but grouped irregularly, sometimes lying almost 

 straight. Length of young individual, twenty-four mm. ; 

 length of longest fragment of adult, forty mm. ; diameter, in 

 excess of two mm. Specimens attached by entire length, up- 



