60 



ANOTHER ABNORMAL SPECIMEN. 



Plale I V, Fuj. 26, (izygous side; Fie/. 27, opposite view. 



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

 it has sixteen arms. The azyKOUS side is uormal and the injury 

 is in the ray opposite the azygous area. The azjgous area is no"j 

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

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

 hut 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 reproseuted in the 

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

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

 and that the ambulacra! openings, which are above the iulerradial 

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

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

 would be, one of the normal varietal forme of B. cogimtxts. And 

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

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

 &i variable as B. variahilis. We think B. cogmdus will never be 

 found with a normal ray having three arms opposite tiie azygous 

 area. But we think the specimen under consideration is a />'• 

 cognaius, and that an injury produced 'the crooked radial series 

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

 is correct, then the abnormal specimen rei^reseuled by figures 24 

 and 25, for additional reasons, belougs to a ninteen or twenty- 

 armed species. 



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

 the collection of A. Albers. 



BATOCRINUS ARGDTUS, Miller & Gurley. 



\_B(docriHus (irgntns, Miller & Gurlpy, 189(», Bull. No. S, 111. St. 

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



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

 each interradial area, tlie 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 scii it looking at the illustration. 



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

 ing a similar form and twonty-oue arms. But the five-armod ray 



