1881.] NATURAL SCIENCES OF PinLADELPHIA. 241 



from the Eifel, which he found to differ from that genus in having 

 no interradials, and, as he supposed, no solid ventral covering- 

 He proposed, in case a separation should be found advisable, to 

 call this form Storthingocrinus. We have no specimens for com- 

 parison, but if the figures are correct, we cannot doubt that these 

 species are not only generically distinct, but belong to a different 

 famil}'. In the entire absence of interradial plates thej' resemble 

 Symbathocrinus, and they seem to have been, like otlier genera of 

 that group, covered exclusively by apical dome plates resting 

 directly upon the external articulating facets of the first radials. 

 We accordingly recognize the genus, but remove it to the Sym- 

 bathocrinidae. 



Edicardsocrinus D'Orbigny, as previously stated, is nothing 

 but a young Platycrinus. Eucladocrinus Meek, is a more mature 

 form in a phylogenetic sense, and is therefore properly separated 

 as a subgenus. 



Platycrinus^ as now restricted, includes species with an anal 

 tube, and those in which the opening is directly through the vault. 

 The tube has been represented by the two Austins and by De 

 Koninck and Lehon as extending almost to the height of the 

 arms, heavy and rounded at the distal end. We fear that some of 

 their figures are more ideal than real ; at least we never saw an , 

 American species with so long a tube. Where we have observed 

 it, the tube is heav}', but short, and we doubt whether in any 

 species it extended to more than two-thirds the height of the 

 arms, if indeed as high. Nor is the upper end closed, as the 

 Austins supposed, nor valvate ; it has a small opening, and this, 

 without being lateral, is somewhat excentric. The opening through 

 the vault, where thei'e is no tube, is located more or less laterally, 

 never centrallj', and usuallj^ at the top of a wart-like process, 

 which may perhaps be considered a rudimentary tube. 



The two Austins attempted a division of the genus, based upon 

 the form of the anus. They proposed to place under Platycrinus 

 only species with a "central 'oral tube ; " those with a " valvate, 

 unobtrusive mouth, or mouth capable of being withdrawn into the 

 visceral cup," they called Gentrocrinus ; and those with a " mouth 

 placed laterally, or not central," Pleurocrinus. Some of these 

 characters are not in accordance with the facts. The so-called 

 mouth, by which they meant the anus, is always excentric, and a 

 withdrawal of the tube into the body, as suggested, is an entire 



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