Chap. X.] 
UPPER SILURIAN ECHINODERMS. 
223 
By far the commonest fossil of this class is the Periechocrinus moniliformis 
(Actinocrinus, Sil. Syst.), PI. XIII. f. 1, 2, the long, bead-like stems of which 
cover the slabs of Dudley limestone, and sometimes attain five feet in length. 
This and the following species have the arms composed of a double row of plates 
set side by side : — Dimerocrinus decadactylus, PL XIII. f. 5 ; D. icosidactylus, 
f. 4, a common fossil j three species of the singular genus Eucalyptocrinites, 
Goldfuss (Hypanthocrinus, Sil. Syst.), found in the Dudley limestone, viz. 
E. decorus (PI. XIV. f. 2), E. polydactylus, M'Coy (a very large species), and 
the rare E. granulatus, Lewis (as yet detected only at Walsall in Staffordshire) ; 
and, lastly, Marsupiocrinites cselatus, PI. XIV. f. 1. A reduced copy of a perfect 
specimen of this fossil is given, Foss. 56. f. 1 ; and at f. 3 the same species is 
drawn without the arms, but showing the long proboscis inserted into the shell 
of a Gasteropod Mollusk, Acroculia haliotis. This shell is better figured in 
PL XXIV. f. 9. 
From the very frequent occurrence of the same shell, tightly embraced by the 
arms of this Crinoid, and from the fact that the mouth of the shell is always 
turned downwards over the proboscis, it is inferred that it was the habitual food 
of the Encrinite. This has long been observed by Mr. John Gray of Dudley, 
who has dissected many specimens from the stone ; and they are to be seen in his 
collection, now in the British Museum. It has also received confirmation from 
the American naturalists Yandell and Shumard, who observed the same habit 
in several of the Silurian Crinoids of America. 
Of those species which have only a single row of joints in each arm, Taxo- 
crinus (Cyathocrinus) tuberculatus is the most common. It occurs of all sizes, 
from the minute specimen represented in PL XIV. f. 6, to much larger forms than 
f. 5. Taxocrinus tesseracontadactylus, f. 4, and T. Orbignyi, M'Coy, are rarer 
forms, the former being found also in Gothland. Cyathocrinus goniodactylus, 
f. 3, C. arthriticus, f. 7, and C. capillaris, PL XV. f. 3, are common Dudley fossils. 
Ichthyocrinus pyriformis, Mill., often grows larger than it is represented in 
PL XIV. f. 8 ; and this species extends its range to North America. Platy- 
crinus* retiarius, PL XIV. f. 9, when perfect, has a long stem with many 
auxiliary arms. Fine specimens are in the Museum of Practical Geology. 
Enallocrinus punctatus, Hisinger, which occurs both in England and Sweden f, 
is frequently found in the "Wenlock Limestone of Wenlock Edge. 
Glyptocrinus ? expansus, PL XV. f. 1, is perhaps one of the most stately species, 
conspicuous for the size to which it grows, and for the numerous plates of which 
its body or cup is composed. 
Lastly may be noted a very common Wenlock fossil, Crotalocrinus rugosus, 
Foss. 56. f. 4-7, whose structure is, perhaps, more remarkable than that of any 
other Silurian Crinoid. 
In most Encrinites the arms issue immediately from the edge of the pelvic | 
cup, commencing with a single joint, and soon branching into two, three, or four, 
the subdivision varying in different species. But in this remarkable Encrinite, 
the upper edge of the pelvis is seen to be surmounted by at least twenty or 
twenty-five arm-joints, instead of the usual five ; and when the specimens have 
lost all but the pelvis and these lower joints, the latter are seen (Foss. 56. f. 5) 
each to have a perforation in their middle as in the arm-joints of all other 
Crinoids. These multitudinous arms soon divide, and subdivide again and 
* Professor de Koninck, on a survey of the I A better nomenclature than that of Miller's 
British Silurian Crinoidea at Dudley, decided (basal plates, radial and interradial plates, &c.) 
that there are several Carboniferous genera is now adopted. See Professor M'Coy in Pal. 
among them. Foss. Woodw. Mus. ; De Koninek et Le Hon, in 
t See Hisinger, Lethaea Suecica, pi. 25. f. 2. ' Les Crinoides Terr. Carb. Belgique,' 1854. 
