1881.] NATURAL SCIENCES OP PHILADELPHIA. 223 



and Edwardsville crinoids, in their general habitus, resemble 

 Burlington fossils, but we have so far not been able to identify a 

 single Burlington species among them, while we found several 

 identical with species from Crawfordsville, though generally 

 smaller. The crinoidal fauna of Canton includes both Bono and 

 Crawfordsville forms, but embraces also some of the huge forms 

 so characteristic of the Upper Keokuk beds of Keokuk, Iowa, and 

 Nashville, Tenn., and which are entirely wanting at Crawfords- 

 ville and Bono. We have not been able to ascertain the exact 

 reUitive age of each stratum, but are inclined to believe that the 

 Crawfordsville bed occupies an intermediate position between 

 those of Bono and Canton on one side, and Keokuk on the other. 



The crinoids to which we allude are easily separated into two 

 groups. Those of the first have flat, somewhat spatulate arms, a 

 subeonical or subturbinate calyx, and a variable arm formula, and 

 are appropriately referred to the genus E retmocrinus, vrhile those 

 of the second, which we refer to Batocrinus, have a globose body, 

 round arms, with arm formula: II, rarely I4. 



Among thirty-two specimens of the first group, all from Bono 

 tliere are twelve which have sixteen simple arms : 44, two others 

 have at one side of the right posterior ray a pair of arms instead 

 of a single arm — the formula may be graphically represented thus : 



1 1 1 111 11-^, and in one specimen we find one of the anterior arms 



1 1 

 represented by a pair, while all the others are simple. The last 



three specimens no doubt are abnormal cases, but they are inter- 

 esting as showing a tendency of the species to an increase of arms 

 in the postero-lateral and anterior ra3's. All the above specimens 

 can be safely referred to a new species which we call Eretmocrinus 

 originarius. 



There are thirteen other specimens, for which we propose the 

 name Eretraocrinus iTj.termedius, which agree with the former 

 in all essential points, having the same peculiar ornamentation, 

 the same form and size, and being derived from the same layers ; 

 but they differ in having, as a rule, in the anterior ray two, and in 

 both postero-lateral rays three additional arms, while the antero- 

 lateral rays are unchanged. The additional arms are given oflT 

 alternately from the two main divisions of the rays as in Actino- 

 crinus. They are simple and in most cases included within the 

 body walls, except in the two posterior raj's, in which the arras 

 arising from the last bifurcation are arranged in pairs. 



