220 CATALOGUE OF THE BLASTOIDEA. 



Locality and Horizon. The specimen is preserved in a light-coloured crystalline 

 limestone of unknown locality. It is said to have come from "Cincinnati, Ohio;" 

 hut this is clearly erroneous. 



ii. Subfamily. S c H I z o B L A ST I D m, E. cC' C, 1886. 



Definition. No anal plate. Posterior spiracles may be fused with the anus. 



Remarks. All the three genera which we include in this subfamily differ from 

 Elmacrinus, and resemble every other Blastoid in the absence of an anal plate. In 

 Acentrotremites and in the only two American species of Schizoblastus which we 

 have seen, the posterior spiracles open separately from the anus, as they do in 

 Elceacrinus (PI. III. fig. 1 ; PI. XIII. fig. 19) ; but in Cryptoblastus and in the two 

 Irish species of Schizoblastus there is a common anal spiracle as in the Pentremitidse 

 (PI. VII. fig. VI.: PI. VIII. fig. 9 ; PL XVI. fig. 12). The other differences between 

 these three genera are expressed in the following scheme. 



A. Spiracles at or near the proximal ends of the deltoids. 



Lancet-plate not completely concealed by the side 

 plates. 



1. Hydrospire-pores along the edges of the i 



• , . *, \ T , , . , , [ Schizoblastus, E. & C. 



deltoids. No hydrospire-plate. J 



2. No hydrospire-pores along the edges of the ) 



, , ., , , , • , , Y Cryptoolastus, &. & U. 



deltoids. An hydrospire-plate. J JL 



B. Spiracles on the radio-deltoid sutures. Lancet-plate ) 



. L . , , . ,, ., , , \ Acentrotremites, L. & C-. 



completely concealed by the side plates. j 



Genus SCHIZOBLASTUS, E. & C, 1882. 



Granatocriniis (pars), Shumard ', Trans. St. Louis Acad. Sci. 18G5, vol. ii. no. 2, p. 375. 



Granatocrinus (pars), Meek and Worthen, Report Geol. Survey Illinois, 18G6, vol. ii. p. 274. 



Schizoblastus (pars), E. & C, Ami. & Mag. Nat. Hist. 1882, vol. ix. p. 243. 

 Gen. Char. Calyx resembling that of Granatocrinus in form, globose, pentagonal- 

 globose, or melon-shaped ; summit contracted and flattened, or a little concave, 

 truncate or slightly protuberant ; section pentagonal, or decagonal. Basal plates 

 almost always confined to the base, but sometimes just visible in a side view. Radial 

 plates may be either very long, or exceedingly short, and incurved below to assist in 

 forming the base. Deltoid plates of variable size, but always visible in a side view. 

 Ambulacra narrow and sublinear, extending along the whole height of the calyx ; 

 lancet-plates sometimes largely concealed by the side plates, though not completely 

 so ; side plates from twenty to about eighty in number. One to four hydrospire- 



J Et auctorum. 



