INTKODUCTTON. 7 



encore dans les grandes cavitcs des bans de coraux, et qu'il ne pent man- 

 quer d'etre d^couvert un jour. II parait en consequence a peu pres certain 

 qu'a notre epoque, il reste encore aux Antilles un representant des Apio- 

 crinidees, fait d'autant plus curieux que je possede de ces iles, une espece 

 vivante de Pentacrinidees, et une Ilolopicrinidee ; en tout trois especes du 

 nieme iarchipel." 



This new genus, Calaniocrinus, is interesting in having the orals greatly 

 reduced, much as in Bathycrinus. It also possesses heavy perisomic plates, 

 passing gradually into still stouter so called interradial plates in Calamo- 

 crinus. in no wise to be distinguished from the true interradials of Paljeo- 

 zoic Crinoids. As will be seen from the description, there are many points 

 in the structure of Calamocrinus which alone so far towards showing: how 

 difficult it is to maintain tlie subdivision into Palaeozoic Crinoids and Neo- 

 crinoids. But that has been abandoned by Carpenter, though we may all 

 feel how convenient for general purposes of discussion such a subdivision 

 would be. 



Liassic Pentacrinidje, Marsupites, and Uintacrinus all have large massive 

 plates between the ra3\s, which, as in Calamocrinus, are nothing more than 

 greatly developed perisomic plates, though they unite the i-ays firmly into 

 a very compact whole. 



The lowest plates (calj-x interradials) have a considerable thickness, and 

 are accurately fitted in between the first and second radials, and they pass 

 gradually into the perisomic plates of the disk, exactly as has been so 

 clear!}- shown by de Loriol in Guettardicrinus, Apiocrinus Roissyanus, and 

 A. Eathieri. 



Waohsmuth has called attention to the significant fact that the vault 

 in the Silurian forms does not acquire that rigid nature which is so 

 characteristic in the Carboniferous, where the vault reached its extreme 

 development. As Wachsmuth has shown, in the Ichthyocrinidte the ven- 

 tral structure is very similar to that of the Comatulae and of Pentacrinus, 

 the nearest approach being found in the Poteriocrinidte, covered ventrally 

 by a perisorae of small irregular plates, and throws considerable light on 

 the question of the constitution of the so called vault of Palaeozoic Crinoids, 

 and on the limits of the actinal and abactinal systems. 



The study of the ventral surface of Calamocrinus and of its interbrachial 

 areas goes far to prove the correctness of the present views of Wachsmuth 

 and Springer, that the rigid vault as it appears in the Subcarboniferous 



