Paleontological Speculations. — Gratacap. 97 
is shown in Syrinsothyris, contrast with the incipient stages of 
growth and structure in the spirifers of the Silurian. 
The strophomenoids from the leptsenoid (Rafinesquina) 
shells of the Silurian show a constant enlargement with vary- 
ing offshoots or auxiliary branches, to the huge Productus 
and Stropheodontas of the Devonian and Carboniferous. 
The first pentameroid shells are small and the later species 
of the Upper Silurian attain magnificent proportions with in- 
creased internal calcifications. 
As the heterogeneous commixture of forms originally 
placed under Orthis have undergone at Dr. Clarke's hands a 
thorough revision and reassortment, their continuity from for- 
mation to formation is considerably broken, and many of the 
new genera are restricted to single formations. But in Platy- 
strophia (Orthis hiforata, O. lynx) there is from the Chaz}^ to 
the Clinton and Niagara, and especially prominent in the Cin- 
cinnati beds (Hudson River) the same obvious increase in size. 
Dalmanella testudinaria of the Trenton strengthens into per- 
elcgans of the Low. Helderberg, Rhipidotnella circuliis of the 
Clinton into R. burlingtonensis of the Carboniferous, Schiso- 
phoria multistriafa of the Lower Helderberg. The atrypoid 
Zygospira becomes later enlarged into the true Atrypas, which 
themselves in the same species (A. reticularis) persistently in- 
crease in size (see Clarke's observations, Pal. N. Y., Vol. 
VHL, pt. n., pp. 167-172). It is unnecessary to pursue a self- 
evident contention further. 
Wachsmuth and Springer have expressed (North Ameri- 
can Crinoidea) in crinoids their unwillingness to construct a 
genealogical tree, "because such representations are generally 
unsatisfactory." But in this very general proposition the evi- 
dence of an inspection of the species from the Silurian to the 
Carboniferous shows conclusively that size and skeletal mass 
increased, and that whether or not "palaeozoic crinoids repre- 
sent, in a broad sense, the larval stages of recent crinoids," the 
movement in massiveness from the Silurian to the Carbonifer- 
ous is, amongst them, evident. The large heavily plated 
Eiicalyptocrinus of the Niagara was a sporadic (Calypto- 
crinidae) and short lived development, but it would be an in- 
supportable hypothesis that Eucalyptocrinus was an unan- 
nounced development. 
