A GROUP OF LARVIFORM GRINOIDS FROM 



LOWER PENNSYLVANIAN STRATA OF THE 



EASTERN INTERIOR BASIN 1 



By J. Marvin Weller 



INTRODUCTION 



Recent collections of Pennsylvanian fossils from Illinois, Indiana, and 

 Missouri have produced a most interesting assemblage of minute larviform 

 crinoids which are unique in comparison with previously known American 

 forms. The only descriptions of fossils with which they are at all compar- 

 able are of specimens collected from Lower Carboniferous strata in Scotland, 

 and Permian beds in the Ural Mountains, and the island of Timor. 



The American specimens which are the subject of this article were col- 

 lected at three localities, namely, eastern Jersey County, Illinois, southern 

 Warren County, Indiana, and in the vicinity of St. Louis, Missouri. In 

 addition to these a single poorly preserved specimen was discovered in south- 

 western Vermilion County, Illinois. All of the specimens except the last 

 were discovered in the laboratory in the course of examining washed material 

 for foraminifera, ostracoda, and other minute fossils. 



These tiny crinoids, the largest of which is less than two millimeters 

 in height, are associated with the abundant fragmentary remains of inoginate 

 crinoids of familiar Pennsylvanian types. It would be natural at first to 

 consider these specimens as representing immature stages in the growth of 

 some of the associated larger and more conventional species, but only a brief 

 examination reveals the fallacy of such a conclusion. The entire construction 

 of the little crinoids is quite distinct from anything previously known from 

 these strata. The most abundant type, for which the generic name Kalli- 

 morphocrinus is proposed (p. 11 ). is monocyclic and without anal plates. If 

 these represent the early stages of any common Pennsylvanian crinoids one 

 or more anal plates, as well as infrabasal plates, should be present. Further- 

 more, the radials in this genus are highly specialized arm-bearers having 

 articular facets suggestive of the Poteriocrinidae. In the majority of the 

 species these plates have developed longitudinal median angulations which 

 give the crinoid a pentagonal or star-shaped horizontal outline and furnish 

 a wider surface above for the articular processes. It is scarcely conceivable 

 that crinoids having such angulated radials could represent the youthful stages 

 of any known species of Pennsylvanian Poteriocrinidae. Also, the specimens 

 of those species which are known from more than a single individual are with 

 few exceptions quite uniform in size and similar in development. If these 

 specimens are immature individuals a gradational series should be obtained 



1 It is with pleasure that I acknowledge the kindness of Mr. J. B. Knight, who has 

 placed in my hands the specimens of three species which he collected in the vicinity of 

 St. Louis, and my indebtedness to Professor J. Wanner of Bonn, Germany, for helpful 

 suggestions and direction to the literature. 



(7) 



