REPORT ON THE CRINOIDEA. 183 
portion of the vault.”? 
I have seen a similar arrangement in well preserved specimens of 
Marsupites, while both d@’Orbigny’ and de Loriol have figured and described the same 
thing in Apiocrinus roissyanus. After stating that there is a considerable amount of 
variation in the interradial areas, even in the same individual, de Loriol says—‘ Presque 
toujours la série commence par une piece unique, hexagone ou 
heptagone, qui est la plus grande, et se trouve encastrée entre les 
premiéres et les secondes radiales, de chaque cédté, reposant sur les 
troncatures des premiéres radiales. Au-dessus il y a deux, trois, 
et méme quatre pieces plus petites, irréguliéres, polygonales, qui 
arrivent au niveau des facettes articulaires des troisiémes radiales, 
une troisiéme et une quatriéme rangée comprennent encore chacune 
trois ou quatre pieces polygonales plus petites, et occupent l’espace 
entre les premiers articles brachiaux ; elles sont suivies par d’autres 
rangées de pitces, plus petites encore, qui paraissent concourir 3 la 
formation d’une votite sur la cavite calicinale.”* De Loriol’s 
enlarged representation of this structure is reproduced in fig 9. 
Here, surely, there was a “dome” as solid as in any Ichthy- 
ocrinoid; but it will scarcely be contended that this dome 
represents the heavy rigid vault of Actinocrinus, rather than the 
plated ventral perisome of recent Pentacrinidee and Comatulide. 
Fic. 9.—Interradial plates of 
Apiocrinus  rowssyanus 
(after de Loriol). Bl, B2, 
first and second brachials; 
Rl, R2, R3, first, second, 
and third radials; pi, 
basal joints of lowest 
pinnule; J, calyx-inter- 
radial, resting on the 
upper angles of two first 
radials (R1); 7, smaller 
interradials, but probably 
; ; : i only perisomic plates. 
The former range back to the earliest Mesozoic times, long anterior 
to Apiocrinus ; and the Liassic Kxtracrinus had a vault essentially similar to that of the 
Apiocrinidz. But there was no regular calyx-interradial resting upon the upper angles 
of the first radials. Its place was taken by a number of movable irregular perisomic 
plates, like those which occur in the same position in Pentacrinus asterius (Pl. XIII. 
fig. 1). They are represented by Miller,* Austin, and also by Quenstedt;*° and were 
continued upwards into those “ which cover the dome-like integument over the abdominal 
pouch,” just exactly as is the case with their fellows in recent forms. 
The Silurian genera Glyptocrinus, Reteocrinus, and Xenocrinus appear to me to have 
been in the same condition; though I will not go so far as to say that the mouth was 
open to the exterior. For the peristome may well have been closed by the more or less 
well defined apical dome plates, which covered the central part of the disk, just as in the 
Ichthyocrinide. The vault of Glyptocrinus is best known in Gilyptocrinus decadactylus. 
According to Miller’ “The regular interradial areas have one plate resting upon the 
primary radials, two in the second range, three in the third, two or three in the fourth, 
1 Revision, part i. p. 54. 
3 Paléont Frang., loc. cit., pp. 272, 273. 4 Op. cit., pp. 57, 59. 
5 Encriniden, Tab. 101, fig. 39a. ® Austin, op. cit., p. 104, pl. xiii. figs. la, 1c, 1h. 
7 Glyptocrinus redefined and restricted, Gawrocrinus, Pycnocrinus, and Compsocrinus established, and two new 
species described, Journ. Cincinn. Soc. Nat. Hist., vol. vi. pp. 220, 221. 
2 Hist. Nat. des Crinoides, p. 21, pl. iii. figs. 1, 3. 
