10 



BULLETIN^ 115, UNITED STATES NATIONAL, MUSEUM. 



is //. discus. In the absence of an}' designation by the author, this 

 shoiikl b,e taken as the type species for that reason. Furthermore 

 Wachsmuth and Springer specifically declared discus to be the type/ 

 and it therefore is the genotype by subsequent designation. H. 

 ■plenissimus becomes the type of a new genus. A third species, 



Fig. 3. — Hadrocrinus. 

 //// = i IJr; WW = i 11 Br; ^ = i III Br; dotted line = R R and Br. 



named by Lyon H. j)e/ntagonus in the text and H. angularis on the 

 plate (fig. c), is founded on a fragmentary detached base, probably 

 belonging to Dolatocrinus grandis. 



The type species is extremely rare, only three specimens besides 

 Lyon's original having been found. Although all imperfect, they 

 exhibit the generic characters very satisfactorih^, showing a wide- 

 spreading calyx, with a low tegmen of rather large smooth plates. 

 The bases of the very heavy biserial arms, restricted in number to 



' N. A. Crin. Cam., 1897, p. :i27 



