4 riiOtJEEDINGS OF THE NATIONAL MUSEUM TOL. 67 



rounding the lumen seems to be a constant feature in Apioc7nnus, as 

 Avell as in some other genera, as for instance, Prolsocrinus A. H. 

 Chirk ^ a Recent member of the same family. It varies from 

 strongly marked and deeply sunken to flush with the rest of the 

 surface. So far as can be ascertained, it seems to be most marked at 

 the top of the stem just beneath the conical enlargement, gradually 

 becoming less marked and finally obliterated below. The flush sur- 

 face of the inner ring resembles the same structure in Apiocj'inus 

 polycryphus, as shown by De Loriol on plate 36, figure 4(2. In com- 

 paring the figures of De Loriol which I have copied with those of our 

 species, it must be remembered that while the former are natural 

 size, the latter are one and a half times enlarged. 



If we had the calyx of our species greater differences might be 

 found. In such a great distance migrational changes are likely to 

 occur. On the other hand, there are crinoid species of intercon- 

 tinental distribution, for example Pentacrinus subangularis^ one of 

 the best known European species, t)f Jurassic age, wdiich has been 

 found in Alaska, with characters so nearly identical that only varietal 

 differences, if any, can be pointed out. And even among existing 

 crinoids, although rarely, an equal extension of range may be found, 

 as in the case of Rhizocrhius lofotensw. which occurs from Florida to 

 Greenland and eastward to Norway. 



»Proc. U. S. Nat. Mus..v()l. :?8. irtlO. p. ^90, fig. 3. 



