165. CONTRIBUTION TO 



HADROCRINUS PLENISSIMUS, Lyon, Rowley. 



Plate 48. Figs. 5, 6. 



Hadrocrinus in many particulars is much like an over-grown Dolatocrinus 

 or as Wachsmuth & Springer assert, like Stereocrinus, in the possession of but 

 one costal. 



The greater depth of the basal concavity involving the plates to the top of 

 the palmars or even higher, the greater width of the calyx and the greater num- 

 ber of dorsal plates, separate Hadrocrinus from both of the above genera. The 

 plates are without tubercles and the radiating linear ornamentation is not 

 strong. 



The columnar funnel is surrounded by a low rounded rim which does not 

 cover the basal plates. The latter are five in number, apparently, but anchy- 

 losed. Wachsmuth & Springer would not commit themselves on the number of 

 basals, but their figure of H. discus shows five sutures, w^hile that of 11. plen- 

 issimus pIiows but three. It is hardly supposable that the number varies in 

 the same genus except in abnormal specimens. From the fragmentary condi- 

 tion of our specimen, nothing further can be ascertained. 



Middle Devonian, Falls of the Ohio. 



DOLATOCRINUS GAEL AT US, M. & G., Rowley. 



Plate 48. Figs. 10, 11, 12. 



The calyx of this crinoid is basket shape with strong radiel ridges knotted 

 in the middle of the plates. There is a large basal pentagon outlined by strong 

 ridges connecting the centers of the first radials. Unlike either D. caelatus or 

 D. arrosus (the latter is a synonym of the former in our opinion) there are no 

 distinct nodes at the interradial centers. 



A few strong raised lines or ridges including between them nodes and 

 toothed lines, pass from the centers of the interbrachials to the centers of ad- 

 joining plates. 



The ornamentation of the ventral disk is large and minute tubercles, the 

 former being near the anal tube and over the arm lobes. 



The specimen is slightly deformed in the region of one arm lobe giving but 

 three arms there and leaving the anal tube excentric. 



Four of the rays support four arras each or nineteen in all. Here then, is 

 a twenty-armed species with nineteen arms. 



Upper Devonian beds. Speed's Cement Quarry, Clark county, Ind 



