RHODOCRINID®. 235 
Infrabasals five, small, pentagonal; forming a flat, impressed pentagon 
at the bottom of a concavity. Basals large, heptagonal, widely truncate 
above. Radials angular at the bottom. Costals two. Distichals 2 X 10 in 
the calyx; the upper ones excavated to form the lower margins of the arm 
openings, of which there are two to the ray,one to each main division. The 
arms are in clusters, delicate, branching and biserial from the last axillary ; 
they either stand erect and fold over the disk, or are pendent, their ventral 
furrows exposed to view. Pinnules rather strong and closely packed to- 
gether. Interradial areas large, composed of numerous plates ; those alter- 
nating with the radials considerably larger and frequently nodose, the 
interbrachials arranged in vertical rows. Anal interradius generally not 
distinct in the cup. 
Ventral disk nearly flat, with five pit-like inter radial depressions, of which 
the posterior one is considerably the largest ; the bottom of the pits formed 
by small polygonal pieces, surrounded by larger plates. In the European 
species, in which the pits are less conspicuous or even wanting, the disk 
plates differ but little in size. The outer margins of the disk are extended 
outward, and form ten large tubular appendages, which are pendent, in some 
species reaching down below the calyx. These appendages are formed either 
by a single row of cylindrical joints, or by three rows of plates longitudinally 
arranged, two of them ventrally disposed, the third dorsally ; but when two 
of them are suturally connected, the consolidated part is composed of two 
and six plates respectively. The tubes are all pierced to their full length 
by a central canal, which, on entering the calyx, connects with the sub- 
tegminal grooves at the inner floor of the disk. In the European species, 
the ten appendages are free from their origin in the calyx, and those facing 
the same interradius are separated from each other by interradial plates. In 
the American forms, however, with the exception of G. spinigerus from the 
Hamilton, and G. fiscellus from the lower Burlington, the tubes meet in pairs 
at midway between two rays, and are for some distance laterally connected 
by a rigid suture; but, although apparently forming a single appendage, 
each one from the base up has its own canal, and the two canals of the same 
set connect with different ambulacra. The arm or ambulacral openings are 
located beneath the appendages; they occupy the bottom of a small, funnel- 
shaped pit, and are formed between the second distichals and the proximal 
plates of the appendages. Anus subcentral, opening out directly through 
the tegmen, and occupying the upper (inner) end of the posterior depression. 
