102 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41. 



comparatively quiet waters of the bays in great numbers, and here, as 

 before described, many lost their lives. The original locality where 

 Uintacnnus was found, in the Uinta Mountains of northern Utah, 

 represents another great bay. In both cases it. is interesting to note 

 that the crinoids are found in the innermost portions of the embay- 

 ments where one would scarcely expect to fuid the concUtions for 

 which Uintacrinus is so obviously fitted. That the water was very 

 shallow in which the beds containing Uintacrinus were deposited is 

 generally conceded. 



Another possible explanation of the formation of these masses is a 

 variant of the foregoing. It may be when gathered in these embay- 

 ments in the breeding season, that the crinoids were thrown together 

 as a result of wind activity. They ma}^ even have been driven into 

 the shallows and there been massed and stranded. The agitated 

 chalk sediment of the bottom would quicldy cover and serve to pre- 

 serve the crinoids. Of the two explanations the former seems the 

 more reasonable, inasmuch as the crinoids are as a rule most beauti- 

 fully preserved and do not show the effects of violent disturbance. 



The whole structure of Uintacrinus as noted above argues against 

 a littoral habitat. The crinoid is evidently adapted only for life on 

 the high seas, for elsewhere storms might well work havoc with the 

 enormous but delicately constructed organism. The widespread 

 occurrence of the genus again argues against a continuous shallow- 

 water life. Living largely in the Gulf Stream, as they probably did, 

 some followed the current and found a final resting place in the 

 European Chalk. It seems possible that the type evolved in Ameri- 

 can waters, and here Uintacrinus cliiefly flourished, a few straggling 

 forms only making their way to the European seas. It is possible, 

 of course, that in Europe the scarcity of the organism is due to the fact 

 that as yet no breeding locality lias been found, and that some day 

 masses of Uintacrinus similar to those found in America wiU be dis- 

 covered in those regions. 



A. H. Clark (1909a) gives quite a different version of the breeding 

 habits of Uintacrinus than that here suggested. According to liim the 

 eggs were laid and fertilized while the animals were moving about in 

 the open sea. His idea can best perhaps be expressed in his own 

 words : 



Now a floating colony of Uintacrinus during a breeding period would be drifted about, 

 as at other times, by the surface currents, the waves, and the wind, just as the medusae 

 are; and, consequently, their embryos would fall over a large extent of territory. By 

 the time the larvie from such embryos as happened to fall uj^on suitable bottom had 

 begun to grow, the parent colony would have drifted to a very considerable distance, 

 unless, of course, the species was an inhabitant of inclosed bays, which, however, tak- 

 ing into account its enormous range, is quite unlikely; by the time the young were 

 ready to discard their stems and swim away, forming a swarm of their own, the parent 

 colony would be in some remote part of the sea. As the position of the parent colony 



