162 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



CRYPTOZONIA Sladen. 



Specialized Asteroidea without true marginal plates. In other 

 words, there are no large and conspicuous marginal plates bordering 

 the animals, but in primitive forms large adambulacrals do margin 

 the species. In other primitive forms more or less of the infra- 

 marginals may be present, but if so they remain adjoining the adam- 

 bulacrals. 



Ambulacrals alternating or directly opposite one another. 



Oral armature generally with the adambulacral elements the most 

 conspicuous; more rarely the ambulacral elements are most promi- 

 nent. 



Contains the following families: 



StenasteridsB. Schuchertiidse. 



Monasteridae. Palasteriscidse. 



Urasterellidse. Schcenasterid^e. 



Calhasterellidse. Palaeosolasteridse. 



Compsasteridse. 



Remarks. — This widely accepted order, which appears as if founded 

 in nature on a single grand phylum, probably has no such value. 

 In other words, as terids without either one or both of the marginal 

 columns bounding the animal developed several times. Therefore, 

 the absence of these ossicles is no indication of dhect phyletic 

 relationship, but such are simply cases of parallel development. As 

 long as asterids retain the primitive characters of few columns of 

 rather strong ossicles and the adambulacral type of oral armature, 

 they are clearly Phanerozonia, but when the ponderous skeleton 

 breaks up into a more flexible one of small pieces, then the marginal 

 and abactinal columns vanish as such in the mass of small plates. 

 On the other hand, ponderosity may even be retained with the loss 

 of the inframarginals alone. In all of these Paleozoic forms, the 

 adambulacral type of oral armature is the rule. 



Among the Paleozoic "Cryptozonia" it seems certain that at least 

 the famihes Stenasteridse, UrastereUidse, Schuchertiidse, and Palseo- 

 solasteridse had independent origins in Phanerozonia stocks. The 

 Urastercllidfe and Calliasterellidfe apparently had a single origin in 

 the Phanerozonia subfamily ^Mesopalaeasterinfe by the adoption of 

 marked flexibility. On the other hand, the families Stenasteridse 

 and Monasteridte retained rigidity and ])rimitive characters, and 

 more probably arose in the Hudsonasteridae through the loss of the 

 inframarginals alone. The Schuchertiidse also had theh origin 

 directly in some Phanerozonia stock and one naturally looks for it 

 in forms developing large interbrachial areas as in the Palasterinida). 

 In this family, however, the accessory plates are introduced between 

 the adambulacrals and inframarginals, while in the former family they 



