On Certain Crinoid Genera. — Springer. 95 
No radianal. 
Arms heterotomous ; iBr few ; large 
anal x followed by other irregular 
plates; 10 main arm-branches with 
branching ramules inside of dich- 
otom Litliorcriints. 
20 main arm-branches, with simple 
ramules inside of dichotom -ivistocyinns. 
Dactylocrinus. 
Arms isotomous ; anals in 2 or more 
irregular series, supported either 
directly on post. B., or on anal x. . .: . . Forhcsiocrinus. 
2. Anal plates in vertical series, often bor- 
dered by small, irregular plates 
Radianal and anal x, followed by others. 
Arms isotomous; iBr few Giwriinocriniis. 
No radianal. 
Arms isotomous. 
Arms simple Rhopalocrinns. 
Arms branching; anals in tube-like 
row Taxocrimts. 
Arms heterotomous ; bearing ramules. 
Ramules unilateral. 
On inside of dichotom, 20 main 
branches Syncrocrinus. 
On outside of dichotom ; 20 main 
branches Oligocrinus. 
Ramules bilateral, branching in clus- 
ters alternately on both sides of 10 
main arm branches Onychochrinus. 
3. Anal side not distinct. 
Arms heterotomous ; simple ramules on in- 
side of 20 main arm-branches ; may 
have iBr IVaclismiithicrinits 
Arms isotomous ; iBr not filling distal face 
of radial Nipterocrimis. 
Some of Angelin's Silurian genera are arranged with 
doubt, especially the very irregular Calpiocrinns. In some, 
specimens the arms abut closely ; in others they are consid- 
erably divergent. I have specimens from Dudley, identified 
as C. cvatns, which have the basals very plain, and show a 
small radianal directly under the right posterior radial; in 
the Gotland specimens I can sec no trace of +his, but the bas- 
als are entirely overgrown and concealed by the infra-basals. 
This Dudley form may belong to a new genus; if so it may 
take the name Leiocnniis. and will fall under the Taxocriu- 
idae, next to Sagcnocrinus. 
