INVERTEBRATES. 227 



the same mass with Crinoid columns, as we often see other fossils. No one, 

 however, we believe, who has had an opportunity to examine a good series of 

 specimens, entertains such an opinion at this time. Indeed, aside from all 

 other reasons for rejecting this view, it seems to be against all analogy to sup- 

 pose these creatures would have been provided with such powerful jaws, unless 

 they were free to seek and devour larger food than the minute floating objects 

 upon which the Crinoids probably subsisted.* 



The existence of jaws in the genus Archeeocidaris is shown in the figures of 

 A. Wortheni of Hall, on plate 26, of the Iowa Report, though no allusion is 

 there made to them in the text. We have also, now, the means of showing 

 Eig. 21. that the genus Melonites was provided with simi- 



lar jaws. The annexed cut (No. 21) represents 

 these jaws as seen in a specimen of M. multipora 

 , — the peristome being somewhat distorted and 

 the jaws displaced by pressure, so as to leave an 

 open space (x) on one side. The dark spaces 

 (ddddd~) between the jaws are slightly restored 

 near the centre of the figure, where the specimen 

 is somewhat defective from accidental erosion. 

 The five radiating lines between these dark bands 

 are suture lines, extending up the middle of each 

 jaw, as we see iii those of Archseocidaris and some 



Oral opening (somewhat distorted) . tti i • • j 



and jaws of Melonites multipora— (nat- recent HjCUinOldS. 

 ural size). 



In the number of Wiegmann's Archives, already cited, Dr. Eoemer gives 

 excellent figures of the general appearance, of Melonites multipora, and of the 

 arrangement of its ambulacral and interambulacral pieces. He also there gives 

 a figure of the apical disc of the same, but the last mentioned figure differs in 

 several respects from the specimens examined by us. In the first place this 

 figure leaves a black ring around the disc, so as not to show the connection of 



* The not unfrequent occurrence of Crinoids, imbedded with the shells of Platyceras 

 and other Gasteropods, in contact with the vault, has led some Paleontologists to the 

 conclusion that in these cases, the Crinoid was in the act of devouring the Mollusk 

 at the moment when it perished. Some even seem to think that the Crinoids actually 

 swallowed these shells. This, however, to say the least of it, would have been a 

 physical impossibility, since the oral opening, when found with its margins entire, is 

 rarely so much as the tenth of an inch in diameter, and is also often placed at the ex- 

 tremity of an elongated, slender tube or proboscis, made up of close-fitting solid plates. 

 We also think it exceedingly improbable that the palaeozoic Crinoids ever preyed upon 

 even the softer parts of such large objects, though we are far from being willing to 

 adopt the conclusion of M. M. Dujardin and Hupe, that they were entirely nourished 

 by absorption over the surface. 



