THE FOSSIL CRINOIP GENUS DOLATOCRINUS AXD ITS ALLIES. 9 



With the incorporation of the lower pinnules in the calyx wall by 

 the growth of interradial structures, the space available for their 

 accommodation became reduced, resulting in more or less displace- 

 ment by crow^ding, packing and overlapping, so that the pinnulars 

 can not always be traced in linear succession, especialh^ at the dorsal 

 side. Some pinnulars w^ell developed at the interior of the calyx 

 wall are smaller exteriorly, or are not seen at all, thus giving rise to 

 confusion w^hen comparing the different views in the figures. Thus 

 the first pinnule, as seen from the ventral side, is plainl}- given off from 

 IIBrj, w^hereas at the dorsal side the lowest fixed pinnular appears 

 to be connected usually with IIB3, sometimes with IIBr4; and the 

 pinnulars connecting with IIBrj and IIBrg are usually not visible at 

 the exterior. I have shown the mode of succession by the diagram 

 (text-fig. 2), made from the ventral side, and the above fact must 

 be remembered when studying it, as well as v^hen comparing the 

 dorsal and ventral views of the calyx in the same specimen shown by 

 plate 1, figures 7, S. The enlargement of the lower pinnulars ven- 

 trally is at the expense of the adjacent plates, and therefore the outer 

 surface of the large iuterbrachial, contrary to the usual rule in the 

 crinoids, is larger than the inner. 



Professor Rowley, in Greene'sContiibution to Indiana Paleontology ^ 

 has described under the name Stereocrinusfdilatus a fragmentary speci- 

 men from the "Upper Helderberg" at the Falls of the Ohio, which 

 may possibly be identicfil with this species; l)ut it is impossible from 

 the figure or description to make out any specific characters, Rowley 

 noted, how^ever, a marked difference between this form and iS'^er6ocfmi/,,<f, 

 and said that if he had better material he would not hesitate to erect 

 a new genus for its reception. 



Horizon and locaHfij. — Onondaga limestone: Louisville, Kentucky^ 

 and Genesee County, New York. 



Genus HADROCRINUS Lyon. 



Plate 2, fig. 1. 



Hadrocrinus Lyon, Transactions American Philosophical Society, vol. 13, 1869,. 

 p. 445-451, pi. 26, fig. a (not h and c). — Wachsmuth and Springer, 1897,. 

 North American Crinoidea Camerata, pp. 327-8, pi. 24, fig. 1. 



Lyon's definition and formula for the genus specified 2 by 5 plates 

 in the first radial series, which in our terms would mean that it has 

 only one primibrach ; and he expressly stated in a note to the generic 

 definition on page 445 that "the formula is intended to receive all 

 crinoids with only two ray-pieces in the primary series. " Although 

 his first species in order of description was H. phnissimus , the only 

 species which agrees with his generic definition in the above character 



» Vol. 2, 1906, p. 8, pi. 3, fig. 5. 



