INDIANA PALEONTOLOGY. i9u 



NUCLEOCRINUS IMITATOR, Rowley. 



Plate 57. Figs. 13, 14, 15. 



This very interesting blastoid was figured and' described in, No. 9 of 

 this series of bulletins. Herewith we figure another specimen showing well the 

 features of the species. The chief characters of jV. imitator are its greater 

 width than depth, concave basal region ; narrow, depressed interradial sinuses 

 and boat-shaped elevations about the ambulacra. The ambulacra are narrow 

 and the ventral region a little concave. 



Specimens of this species in a casual way strongly remind one of Orhitre- 

 mites norwoodi. 



The distal ends of the ambulacra are received into little foot-like folds that 

 project obliquely outward. 



Hamilton group, Speed's Cement Quarry, Clark county, Ind. Collection 

 of Mr. G. K. Greene. 



DOLATOCRINUS E XC A V AT U S, W. & Sp., Rowley. 



Plate 57. Figs. 16, 17, 18. 



Figure 16 is a specimen that has but one costal in one of the radial rays. 

 It will be observed that while this one costal is somewhat longer than the 

 second costal, in the other four rays it is not as deep as both costals in those 

 rays, but the distichals are a little larger. 



Figure 17 is a somewhat larger specimen with unbroken radial ridges and 

 two rays with single costals, perhaps three rays. A disarrangement of plates 

 about the latter ray leaves us in doubt as to whether it has two or three plates 

 in the first series. If three, then the two costals have much less depth than in 

 the two rays that do have three primary plates. 



"We have seen other specimens of this same species with but two plates in 

 the first radial series and yet species have been founded upon characters of less 

 importance. 



In a great series of specimens of this species with the tendency to reduce 

 the number of primary radials, doubtless specimens can be found with but a 

 single costal to each of the five rays. Could such specimens belong -to Stereo- 

 crinus? 



Number 18 has a small but distinct piece lying between the second costal 



