NATURAL SCIENCES OF PHILADELPHIA. 59 



racter of the vault-pieces around its base, probably also spiui- 

 ferous. 



Height of body to arm-bases, 0.47 inch ; do. to top of vault, 

 0.60 inch ; breadth, 0.95 inch. 



This species differs so materially from D. lacus and D. Marshi, 

 of Lyon, in its ornamentation and other characters, as to render 

 a comparison unnecessary. The only other described species from 

 the same horizon, known to me, D. lamellosus (= Cacahocrinus 

 lamellosus, Hall, Fifteenth Report of Regents, p. 141), must also 

 differ materially, as it is described as having tlie body "spreading 

 horizontallj'- to the top of the third radial plates." It also has 

 four arms to each ray, instead of only two, as in our sjiecies, which 

 likewise differs in the details of its ornamentation. 



It is probablj" more nearly allied to some of the other species 

 described by Prof. Hall from the Hamilton Group, under Troost's 

 name Cacaboeriiius, though it seems to differ from them all in 

 details ; while the limited vertical range of the species of Cri- 

 noidea, renders it extremely improbable that the same species 

 would be found in both the Corniferous and Hamilton groups. 



It may be proper to remark here that thei'e is no difference 

 between Dolatocrinus^ Lyon, and Cacahocrinus^ Troost. It is 

 true, Mr, Lyon gives five as the number of basal pieces in his 

 genus, but he also stated in a note that it may have only three 

 basals, as he had not seen specimens showing the structure of the 

 base very clearly. Troost's genus, as published from his manu- 

 script, after the date of Mr. Lyon's publication of Dolatocrinus, 

 agrees exactl}^ with the characters assigned the latter, excepting 

 in having only three instead of five basal pieces. The species 

 here described, however, is certainly a typical Dolatocrinus^ and 

 yet shows only three basal pieces. 



For the use of the fine specimen affording the above characters, 

 the Survey is under obligations to the Rev. Mr. H. Hertzer, of 

 Columbus, Ohio. 



Locality and position. Columbus, Ohio. Corniferous division 

 of the Devonian. 



1871.] 



