UINTACRINUS: ITS STRUCTUKE AND RELATIONS. 11 



cit, p. 118) says that Antedon Sarsi was brought up in thousands by the 

 '• Blake." Professor Verrill, in his account of the dredgings of the " Fish 

 Hawk " for the U. S. Fish Commission,'^ says that Antedon Sarsi was found 

 off the coast of New EngLand in such profusion that over ten thousand 

 specimens came up at a single haul of the dredge. A mass of Crinoids 

 like this, suddenly killed, and settling upon a quiet, chalky, or muddy 

 bottom, and becoming embedded there, would produce just such a limestone 

 plate, with specimens preserved intact on the lower side, as those of 

 Umtacrimis. 



A similar mode of occurrence prevails with other Mesozoic Crinoids. 

 In the Lias immense colonies of Pentacrinus fossilis (P. hriareus) are found, 

 whose remains form limestone bands of considerable extent. The Austins, 

 in their Monograph of Recent and Fossil Crinoids, figure — at the end of the 

 text, without number — a beautiful slab of this species, which shows very 

 clearly how they occur. Professor Jaekel t states that the unstalked Sacco- 

 comce, from the upper Jurassic lithographic slate at Solenhofen, lie so thickly 

 together that twenty or more specimens may be counted on a slab the size 

 of a hand, and that they must have lived in that sea in such prodigious 

 numbers that he reckons them by millions. 



So far as observed among the recent Crinoids, each one of the colonies 

 consists of but a single species. Carpenter, in the ^^ Challenger" Report on 

 the Stalked Crinoids, pp. 139, 141, says, that the two species of Rhizocriniis 

 w^ere never found at the same station, either by the " Blake," the " Chal- 

 lenger " or the '' Porcupine." 



I have used the word -^ colony " in referring to the aggregations of 

 these Crinoids as we find them. It seems to me this must be understood 

 a little differently from the sense in which it is generally used in this con- 

 nection. It could scarcely have been the ordinary condition in which the 

 Uintacrinus was living, like the Pentacrini growing upon the sea-bottom, or 

 the Comatulse as they herd together among the rocjvs and coral reefs of our 

 present shores. These Crinoids w^ere in detached masses, clinging together 

 and floating in the open sea, entirely separate from other objects. They 

 were actually swarming, very much like a sw^arm of bees when they leave 

 the hive and settle upon some object, — some on the outside and some 

 buried underneath their fellows, — all in the utmost confusion. It must 



* Am. Jour. ScL, Tebruary, 1882, p. 135. 



f Ueber Flicatocriniden^ Hi/ocrinus uad Saccocoma, Zeitsch. d. Deutscli. Geol. Gesell., 1892, p. 684. 



