Oil Certain Criiioid Genera. — Spri>iger. 89 
slender. Interbrachial spaces not depressed, filled with closely fitting 
plates in several ranges. Anal side differing from the others by its 
distinctly greater width and more numerous plates ; by the presence of 
a large anal plate resting upon the posterior basal ; and of a radianal, 
lying between the upper corners of the two basals, and about half way 
under the right posterior radial. The anal plate .r is supported in the 
angle formed by the radianal and the posterior basal. Sutures in the 
radial series and arms strongly arcuate, and patelloid processes promin- 
ent. Stem composed of alternate thick and thin plates except near the 
calyx, where there are several thick ones in succession, without any 
marked taper. 
Some specimens from Dudley, England, strongly resemble this spec- 
ies in the straightness of the sides and flatness of the plates ; but thej' 
lack the patelloid processes, a,ild the position of the radianal is differ- 
ent. In the English specimens the radianal enters the basal ring and 
rests upon the infrabasals ; while here, instead of entirely separating 
two basals, it rests between their upper corners, and does not touch 
the infrabasals. If this should prove constant in a number of speci- 
mens, it might require their separation generically from the typical 
species, 5". cxpansiis; but without further materia] this is not deemed 
advisable. The stem in our species agrees with that of 6". ex{>ansus 
in not having the rapid taper and thin columnals at the proximal end, 
which is characteristic of the group generally, except a few Silurian 
forms. 
The presence of the large radianal is the important generic 
character of this form. The genus Sageiioeriiius was treated 
b}' the Austins as allied to the Actinocrinidae. Von Zittel, in 
1879, placed it with the Glyptocrinidae ; while Wachsniuth and 
Springer, in 1881, arranged it under the Rhodocrinidae. Sub- 
sequently, after seeing specimens which showed that it is 
not a Camarate crinoid, w^e referred it to the Tchthyocrinidae, 
being the division now called Flexibilia Impinnata, where it 
undoubtedly belongs. It was thought to be closely related to 
t'.ic form for which De Koninck and Le Hon established the 
gCJius Forbesiocrinus. I have since then* expressed the opinion 
chat De Doninck and Le Hon's gemi> would have to be given 
U|j, and also that the American species referred to it — such 
as F. agassiai — might fall under Sageiiocriniis. Further in- 
vestigation of these forms, in connection with a ^lonograph of 
the Impinnata division of the Crinoidea Flexibilia, has con- 
vinced me that this opinion was not well founded, and that 
on the contrar}', not only are the species described under 
Forbesiocrinus generically distinct from Sageiiocriniis, but the 
• Vintacrinus. Mem. Mus. Comp. Zool., Vol. XXV, No. 1, p. 71. 
