1881.] NATURAL SCIENCES OF PHILADELPHIA. 179 



III.-SPHiEROIDOCRINID^. 



The above name is proposed as a family designation, to include 

 such forms of the Palaeocrinoidea, in which both calyx and vault 

 are constructed of a large number of immovable plates and these 

 forming inflexible walls ; with several orders of radials, and one or 

 more of interradials on both the oral and aboral sides. The 

 SphferoidocrinidiB differ thus conspicuously from the Ichthyo- 

 crinidte with their flexible walls and squamous vault, and from the 

 Cyathocrinidffi with their uniform elements of three rings of 

 plates in the calj^x, without interradials, and with simple oral 

 plates in the vault. 



The family, as thus defined, will include genera with underbasals, 

 and genera without them. In this we differ from most authors, 

 who make the presence or absence of these plates a marked family 

 distinction, and who place together within the same family Cj'a- 

 thocrinidte, Ichthyocrinidse and Rhodocrinida?. 



Pictet, Traite de Paleontologie, vol. iv, included in his " Cya 

 thocriniens " our Cyathocrinidee, RhodocrinidiB and parti}' our 

 Ichthyocrinidae ; from the former, however, he excluded Graphio- 

 crinus, which had been described by De Koninck and Lehon with 

 a single circle of plates beneath the radials, and from the latter 

 Fo7'beswcrinus and Taxocri7ius, in which underbasals had not been 

 discovered ; while he admitted the allied genera Ichthyocrinus, 

 Lecanocrinus and Mespilocrinus in which they had been observed. 

 Similar opinions were held by d'Orbigny, Hall, Miller, Austin 

 and others, not including, however, Roemer and Schultze, who 

 made the Rhodocrinidte a distinct family. 



In the first part of this work we have discussed somewhat fully 

 the relations of the underbasals, which we took to be the product 

 of growth in geological times, introduced gradually by interpola- 

 tion between the basals. It is very remarkable that, although the 

 introduction of underbasals dates back to the Lower Silurian, as 

 a rule, the genera in which those plates are found differ at no time 

 materially from those in which they are wanting. Even as late 

 as the Subcarboniferous, we find such species as Adinocrinus 

 Whitei, and Bhodocrinus Wachsmuthi, both from the Burling- 

 ton limestone, so strikingly similar in every respect, both in the 

 structure of the bodj^ and arms, that the species cannot be 



