On Certain Lrinoid Genera.- — Springer. 97 
seen a decided tendency toward pinnulation. which may lead 
up to the Pinnulate division of the Flexihiha. 
The FlexibiHa Tmpinnata form a compact, well defined 
group ; limited, so far as we know, to Palaeozoic time. The 
two families of this group range from the Lower Silurian to 
the later Carboniferous ; and they exhibit, to some extent, a 
succession of parallel modifications. There is a general ten- 
dency from irregularity toward regularity in the calyx. struc- 
ture. The radianal, which is well developed in Silurian gen- 
era of both families, disappears from both in the Carbonif- 
erous. Bilateral symmetry, as characterized by the presence 
of a tube-like series of anal plates, is carried through al- 
most the entire Palaeozoic in Taxocrinus^ and is perhaps most 
strongly marked in one of the latest developed and latest sur- 
viving genera — Onyelioeriniis. As occurs in other groups, 
the simplest form of all — Ichthyocrinus — with a perfectly 
symmetrical calyx, without interbracbials, is the longest 
lived genus, ranging from the Silurian to the Coal Measures ; 
and is the last survivor of the group, so far as at present 
known. 
In studying this group, I have found a most remarkable 
example of recuperation. It is a Ta.vocriniis, in which the en- 
tire calyx, wnth the exception of the infrabasals and one basal, 
has been broken off during life and restored by new growth. 
The stem and plates above mentioned are those of a medium 
sized crmoid, while the recuperated calyx is that of a very 
young one. There is considerable irregularity ; e. g. it has 
six rays, one having apparently been developed on the anal 
side. This is the first instance of recuperation of more than 
a ray that I have observed among fossil crinoids. Daniels- 
son, in his Report on the Crinoidea of the Norwegian North- 
Atlantic Expedition of 1876-8, has described three speci- 
mens of Bafliycrinus ear pe uteri from the Arctic ocean, in 
which recuperation of the crown upon the basals has taken 
place. — thus producing the crown of a verv young crinoid 
upon a verv mature stalk and liasal ring (Op. eit. pp. 11-13, 
PI. Ill, figs. 1-2: 3-4; 5-6). 
