19 



shallow, or nearly flat, subtriangular in outline ; arms bifurcating upon 

 the second radials, -which are short, but cover the whole facet of the 

 first radials, and are continued as a compound arm by two pairs of 

 short, strong arm-plates, abutting each other by their inner sides, up- 

 on the last pair of which the arms again bifurcate ; a high, narrow, 

 tumid inferradial plate rests in each of the retreating angles, formed 

 by the upper slopes of the first radials, against which the dome-plates 

 and those which arch over the compound arms abut ; these latter plates 

 are tumid or subspinose. Anal series consisting of one rather large 

 plate resting in the angle between the first radials, which is surmounted 

 by numerous small plates surrounding the anal opening, which is situ- 

 ated about half way between the first radials and the summit of the 

 dome. 



This species resembles P. pileaius of Goldfuss, as figured by De Ko- 

 ninck and Le Hon, in " Recherches siir les Crinoids du Terrain Car- 

 honifere de la BeJgique" PL VI., fig. 3, but differs in the truncated 

 and nodose base, the different shape and proportions of the arm-plates 

 and articulating facets of the arms with the first radials. 



Locality and position, in the upper division of the Burlington 

 Limestone, Burlington, Iowa. — Collection of Mr. Charles Wachs- 

 muth. 



Genus Dichocrinus Munster. 



DiCHOCRiNUS ANGUSTUS (n. s.) Body rather small, about twice as 

 high as wide, in the form of a narrow, slightly truncated cone; basal plates 

 higher than the diameter at their junction with the first radials, sloping 

 direct to the column, which is small and round ; first radials and anal 

 plates of about the same size, nearly twice as high as wide ; the anterior 

 first radial and first anal plates a httle widest below : arm-facets occu- 

 pying the greater part of the width of the first radials, very slightly 

 excavated and narrow ; second and third radials short, with two indis- 

 tinct nodes abreast on each; arms bifurcating on the third radial, and 

 continued by two short plates, which are also indistinctly nodose to the 

 second bifurcation, beyond which the arms are composed of a single 

 series of small plates with slightly oblique sutures. Surface apparently 

 smooth. 



This species differs from D. scitulus of Hall in its much greater pro- 

 portionate length, with its plates differently proportioned ; the place 

 of attachment of the column is round, and not protuberant and oval, 

 as in that species. It is the smallest described species in these rocks 

 except D. pocillum. 



Locality and position, in the upper division of the Burlington Lime- 

 stone, Burlington, Iowa. — Collections of Mr. Barris and Mr. Wachs- 

 muth. 



Dichocrinus crassitestus (n. s.) Body obconical, spreading with 



