66 



ANOTHER ABNORMAL SPECIMEN. 



Plate IV, Fig. 26, azygous side; Fig. 27, opposite view. 



The general form of this specimen is that of B. cognatus and 

 it has sixteen arms. The azygous side is normal and the injury 

 is in the ray opposite the azygous area. The azygous area is not 

 exactly like a typical area in B. cognatus, because it is wider, in 

 the superior part, and the plates ere somewhat differently arranged, 

 but it is near enough to that species to classify it there, unless 

 for another reason it belongs elsewhere. The ray opposite the 

 azygous area is bent out of shape, the plates are displaced, 

 and it bears three arms. The arm formula, as represented in the 

 specimen, is 3+3+3+4+3. Suppose the ray were straightened 

 and supported only by two arm openings directly in line with it, 

 and that the ambulacral openings, which are shove the interradial 

 area, on the left, belonged to the ray on the left, the arm formula 

 would he 3+4+2+4+3, which would represent, what we suppose 

 would be, one of the normal varietal forms of B. cognatus. And 

 it may be, after all, that the interior will show that to be the ar- 

 rangement of the ambulacral canals. If so, it makes B. cognatus 

 as variable as B. variabilis. We think B. cognatus will never be 

 found with a normal ray having three arms opposite the azygous 

 area. But we think the specimen under consideration is a B. 

 cognatus, and that an injury produced the crooked radial series 

 and displaced the ambulacral openings to the vault. If this view 

 is correct, then the abnormal specimen represented by figures 24 

 aud 25, for additional reasons, belongs to a ninteen or twenty- 

 armed species. 



Found in the Burlington Group, at Burlington, Iowa, and now in 

 the collection of A. Albers. 



batocrinus argutus, Miller & Gurley. 



[Batoorinus argutus, Miller & Gurley, 1896, Bull. No. 8, 111. St. 

 Mus. Nat. Hist., p. 9, pi. 1, fig. 8 aud 9.] 



The type of this species has twenty-one arms, two plates in 

 each interradial area, the second one small, and six plates in the 

 azygous area, 1+3+2. The five-armed ray is on the left of the 

 azygous area as we sea it looking at the illustration. 



Mr. F. A. Sampsou has a specimen from the same locality hav- 

 ing a similar form and twenty-one arms. But the five-armed ray 



