REPORT ON THE CRINOIDEA. 187 
remain altogether undeveloped. The apical system consists of a dorsocentral plate, 
basals, and radials, with the frequent addition of under-basals and interradials. These 
plates form a cup, which either simply supports, or more or less completely encloses the 
visceral mass, and often bears jointed appendages, the arms and pinnules. 
An oral system, consisting of a central plate (orocentral) and five orals is developed 
above the peristome of the larva to a very variable extent, and may be either altogether 
resorbed, or reach a high degree of importance by the appearance of additional plates so 
as to form a vault or “tegmen calycis.” The anus is situated on the oral surface, which 
may be bare, or more or less covered by calcareous plates. The water-vascular ring does 
not communicate directly with the exterior, and the lateral branches of the radial vessels 
(when present) are respiratory, but not locomotor in function. 
Class 1. CRINOIDEA, Miller, 1821. 
Crinoidea, Auctorum. 
Stilasterite, Goldfuss, 1826-1835. 
Asterencrinidea, de Blainville, 1834. 
Pinnigrada, Forbes, 1841. 
Pinnastella, Austin, 1842. 
Brachiata, Burmeister, 1856. 
Actinoidea, Roemer, 1856 (Date of Preface). 
Encrinide, Quenstedt, 1876 (Date of Preface), 
Eucrinoidea, Zittel, 1880 (Date of Preface). 
Definition.—Pelmatozoa, in which the radial plates of the calyx bear more or less 
branching arms. ‘These consist of segments which are articulated by means of muscles 
and ligaments, and in most cases bear similar jointed appendages, the pinnules. The 
nervous system consists (1) of a central organ situated in the calyx, and fibres 
extending from it through the skeleton of the stem, arms, and pinnules; (2) of a 
circum-oral ring and radial extensions which are in close relation with the ciliated 
epithelium of the ambulacral grooves. These are more or less extensively distributed 
on the ventral surface of the disk, arms, and pinnules; and are bordered by groups of 
tentacles which alternate on opposite sides. -When they are absent, the radial water- 
vessels give off no tentacular branches. The water-vascular ring opens by five or more 
water-tubes into the body-cavity, which itself communicates with the exterior by a 
corresponding number of water-pores. The mouth is central, except in one genus, and 
the anus subcentral or excentric. The genital glands are lodged in the lower parts of 
the arms, but are usually fertile only in the pinnules. 
Remarks.—Various writers have attempted at different times to separate the Crinoids 
and their allies from the remaining classes of the Echinoderms by somewhat more definite 
characters than those which distinguish these various classes inter se. Very little was 
