12 Echinoderma. 



Camerata. The anal tube seems to have been more highly organised than that of 

 the Camerata generally, and to approach that of the Fistnlata in its construction. 

 Beneath the overhanging lateral margins of the proximal plates of the rays are five 

 interradial chambers. In C. each of these contains two sets of laminated structures 

 which were regarded by Angelin as part of a consolidating apparatus. Each set 

 consists of 5-7 upright folded lamellae attached at their lower ends to the inner 

 surface of the first radials, and closely resembling the hydrospires of Oropho- 

 crinus. Nothing like this structure occurs in any other known Crinoid. 



Keyes fl ) mentions numerous species of Palseocrinoids. mostly Camevata, which 

 have been found with a Gasteropod (Platyceras\ attached to the vault. Only two 

 of them have a prolonged anal tube or proboscis , and the anterior end of the 

 shell is always stationary at the edge of the anal opening, from which the poste- 

 rior end is carried backwards with the growth of the shell. The Platyceras does 

 not seem to have been parasitic in its habits, though probably obtaining the greater 

 portion of its food from the excrementitious matter of the Crinoid. 



Keyes 2 ) points out that Echinoderm life during the Lower Carboniferous period 

 in the Mississippi basin was preeminently dual in its general aspect, the Crinoids 

 predominating greatly during the first part, and the Blastoids during the latter 

 part of the period. The culmination of Crinoid life in the middle of the period is 

 indicated by the great variety of form and the extreme specialisation of particular 

 anatomical structures. Towards the close of the Keokuk nearly all the specialised 

 forms became extinct, the later Carboniferous Crinoids being more generalised 

 types which are ordinally related to living forms. These facts suggest decided 

 and wide-spread changes in the biological and physical conditions of environment. 



Ringueberg has proposed a revised analysis of the calyx in the Calceocrinidae. 

 The two plates which were described by Wachsmuth & Springer in Calceocrinus 

 as paired anals supporting a heavy ventral tube are the two posterior radials. 

 armless, but not absent as hitherto supposed. They support the azygous plate 

 which bears the anal tube, and is the result of an anchylosis and modification of 

 the azygous of the primitive forms with the first anal. In Proclivocrinus (n. g.) 

 the azygous is large and T-shaped, so as to separate the posterior radials. These 

 have no arms , of which there are therefore only 3. as in Calceocrinus. But in 

 Castocrinus (n. g.) there are 4. Each posterior radial bears a brachial. and a 

 narrow azygous is placed between these two posterior brachials which extend 

 downwards between it and their radials. The right brachial is followed by others 

 which make up the fourth arm; but the left supports the anal plate with the ven- 

 tral tube above it. The ancestral form of this family was probably five-armed ; 

 but whether an arm was lost before or after the Crinoid assumed the pendulous 

 position of its calyx cannot yet be determined. The four- armed CW.-stage was 

 followed by one like Prod., in which the cross-bar of the T represents the first 

 anal, and the stem the remains of the azygous; while in Calc. the modification 

 has gone still further, and the stem has become absorbed entirely, only the cross- 

 bar remaining in this, the most specialised form of the family. 







III. Asteroidea. 



See also Bury, supra, p 4, Cuenot. supra, p 6, Fewkes ( 2 , 3 ), supra, p 7, 

 Korschelt, supra, p 3, Kowalevsky, supra, p 5, Mac Munn ( l , z ) : supra, p 6, Se- 

 mon ( 1 ). supra, p 5, Sluiter. supra, p 8. 



The elaborate report by Slatien on the Challenger Starfishes, although mainly 

 systematic . contains descriptions of several new anatomical features , and the 

 author proposes a new classification of the group which is based on factors of 



