246 
Arms, simple after their first bifurcation on the articular 
primary radial ; or bifurcating more frequently ; composed of 
very elongate ossiculae. 
Forming a brachial system of the most meagre description 
when compared with some of the allied genera* ; and quite 
incapable of being brought together into a closed plume. 
The fossil Avhich was figured by MM. Austin under the 
name of Poteriocr'uius tenuis, may serve as the type of this 
genus. The general facies of the crinoid will readily distin- 
guish it from the members of the allied groups. Its very elon- 
gate calyx, the single free-radials, and the simple arms with 
very elongate ossicula}, present together an array of characters 
well worthy of being regarded as of generic value ; and when 
compared with the true Poteriocnnus-fovms, are indicative of 
morphological features of greater divergence than relationship 
within a single genus would reasonably admit. The following 
species will pertain to this genus. 
Dactylocrinus loreus, mihi. 
Poteriocrinus tenuis, Austin (non Miller), Monog. Rec. and 
Foss. Crinoidea, pi. 10., fig. 5. 
A comparison of MM. Austins' figure with that given 
by Miller in " A IN'atural History of the Crinoidea," clearly 
shows that the fossil of the former authors (apart from the 
inaccuracy of drawing ascribed by them to their predecessor), 
cannot be included in the same species, and that, consequently, 
another nomen triviale is required. 
Dactylocrixus tenuis (Miller), Sladen. 
Poteriocrinus tenuis. Miller, Nat. Hist. Crinoidea, p. 71, 
pi. 21, 23. 
Poteriocrinus isacobus, Austin, Monog. Rec. and Foss. 
Crinoidea, p. 74, pi. 8, fig. 4a, 4b. 
* From oui- present Icnowlodge it is impossible to say whether this was in any 
way compensated for by a larger development of pinnulse ; although such might be 
very naturally inferred. 
