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SILURIC AND DFAOXK CVS'I'IDKA 



207 



ANOMALOCYSTITES (?) DISPARILIS Hall 



Anomalocystites disparilis Hall, Nat. Hist. N. Y., Pal., m, [859 [1861], 

 p. 145, pi. 88, figs. 1-4.- Woodv\ \Ki>. Geol. Mag., dec 11, vn, [880, p. 

 [93, pi. (», figs. 2, 3. 

 Of this species the writer has seen eight specimens, six of which 

 were collected by Mr. Hartley and two by Mr. Perdew. These per- 

 mit the exact determination of the thecal plates, and the position of 

 the two spines, all of 

 which are shown in the 

 diagrams in figure 22. 

 Detail of spines and col- 

 umn and the surface 

 ornamentati< in u n de ter- 

 mined on account of 

 the pseudomorphous con- 

 dition of the fossils. 



Length of largest theca Fig. 22. — Analysis of both sides of Anomalo- 

 28 mm.' width l8 mm.' c y st > tes (?) disparilis Hall; natural size, (a, 



depth in basal region 13 

 mm., and in anterior re- 



The ventral side with the plates projected on a 

 plane; b. the dorsal side with the free arm facets 

 shown at a, a. The black spot indicates the 

 probable position of the anus.) 



gion 7 mm. 



Anal side convex, with 

 more or less abrupt sides. Anterior side but slightly excavated, 

 regularly or irregularly, with the lateral margins sharply elevated. 



This species is easily separated by its larger size, more elongate 

 and narrower theca, and the greater convexity of the anal side. 



It is not yet established that A.(?) disparilis actually belongs in 

 the genus Anomalocystites. In the genotype there are 2 arms with 

 imbricating plates, while in the Oriskany species these are apparently 

 replaced by spines of 1 piece, as in Placocystitcs. Further, in 

 A.(?) disparilis the theca between the spines has a large, elongate- 

 quadrate opening, which, in the best-preserved specimen, is about 

 half closed by an inclined plate extending from the anal side over the 

 aperture. In this specimen the longer edges of this opening are 

 striated, suggesting a pectinirhomb. However, as all the specimens 

 are poorly preserved siliceous pseudomorphs, one can not make out 

 the exact nature of this opening. The differences pointed out be- 

 tween A. cornutus and A.( ?) disparilis seem to indicate that the two 

 species may not belong to the same genus. 



Formation and locality. — Found in the upper half of the Oriskany 

 sandstone associated with the Spirifer arenosus fauna. It is probably 



