THE FOSSIL CRINOID GENUS DOLATOCRINUS AND ITS ALLIES. 37 



diameter shows no material departure from the typical characters. 

 The perfectly smooth surface, without sculpturing or any other mark- 

 ing except a small node or spine on the first (sometimes second) 

 ])rimibrach, which exceptionally also develops into a keellike ridge 

 as in D. spinosus; and the j^eculiar cordate shape of the first inter- 

 brachial, with its usually wide distal margin for the support of the 

 very large second plate (excepitionall}' angular and supporting two 

 plates as in D. grandis); are characters which readily differentiate 

 the species from all others. 



A somewhat crushed calyx with ])art of the smooth tegmen intact 

 shows the arrangement of the pinnule openings, four or six to each 

 intersjiace between the 20 arms; it shows that the general form of 

 the calyx was broad and low, somewhat constricted below the arms, 

 with a truncate or broadly curving base containing a relatively 

 small basal pit. In this the basals are seen to be more or less obso- 

 lete, encroached upon and much of their substance resorbed and 

 rej)laced by the large stem-lumen, analogous to the case of Hadro- 

 crlnus. In three specimens the nodes on the radials have enlarged 

 into high, keeled ridges, and in one they are produced into sharp 

 spines — variations which are immaterial in view of the strong domi- 

 nant characters of the species. 



Horizon and locality. — Onondaga (Jefferson ville) limestone: Louis- 

 ville, Kentucky, and vicinity. 



DOLATOCRINUS EXSTANS, new species. 



Plate 10, figs. 8, 9. 



In this species we have a complete departure from the usual hab- 

 itus of the genus in the presence of a strongly protuberant base, 

 instead of the usual concave or flat condition. It is jH'oposed upon 

 the evidence of eight specimens, which were found by the late George 

 K. Greene, in the Onondaga formation at the Falls of the Ohio, near 

 Louisville. They were obtained during a season of low water, aU 

 from the same layer and rather near together, the form being entirely 

 new in the experience of the collectors of that locality. The speci- 

 mens are all more or less crushed and imperfect, but indicate a calyx 

 of large size — probably 65 or 70 mm. in diameter — and having at 

 least 6 arms to the ray, or 30 (perhaps more) in aU. The plates of 

 the dorsal cup have usually a conical central elevation. Correlated 

 with the protuberant base is the presence in the tegmen of long, 

 sharp spines, some of them 25 mm. in length. The interbrachials are 

 of the typical form for the genus, with an occasional irregularity — 

 the large plate of the first range being sometimes 1 1-sided on account 

 of contact with tertibrachs. 



Horizon and locality. — Onondaga (Jefferson ville) limestone: Louis- 

 ville, Kentucky, and vicinity. 



