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SILURIC AND DKVONIC CYSTIDEA 



2^1 



passing to the left of it. In another basally compressed individual, 

 both ambulacra arc bowed toward the anal .side, particularly R IV, 

 causing the opposite side of the theca to be more convex and almost 

 angulated on the left. 



Formation and locality. — Common in the Keyser quarries, where it 

 was first collected by Robert H. Gordon of Cumberland, Maryland. 

 The species is named for its discoverer in recognition of the very 

 valuable services he has rendered, not only as an enthusiastic col- 

 lector, but also as a careful student of the complicated geology of 

 western Maryland. 



Cat. number 35,071, U. S. N. M. 



PSEUDOCRINITES ABNORMALIS n. sp. 



(Plate XXXV, figures 10-12) 



Length of the only specimen 29 mm. ; width 22 mm. ; depth 14 mm. 

 For general form, shape of individual plates and their ornamentation, 

 see the figures and diagram, figure 30. 



Pectinirhombs about equally large and each has from 65 to 70 

 folds. Basal pectinirhomb on plates 5 and 6 and not, as usual in 

 this genus, on plates 1 



<b 



Fig. 30.- 



and 5. In other words, 

 this pectinirhomb is con- 

 fined to the second circle 

 of plates and is not di- 

 vided, one-half of the 

 rhomb being in the basal 

 and the other half in the 

 second row. 



Ambulacra as in P. 

 gordoni, with about 34 

 brachioles on one side of 

 each ambulacrum. 



Comparisons. — This species has the general expression of P. gor- 

 doni, except that the outline of the theca is regularly oval instead 

 of nearly circular. It differs, also, in having the basal pectinirhomb 

 on plates 5 and 6 instead of on plates 1 and 5. That the two forms 

 are really closely related is shown by the arrangement of the anal 

 plates. In P. abnonnalis, as in P. gordoni, these are composed of 2 

 complete circles of plates, while in the group typified by P. clarlci the 

 outer circle consists of plate 13 and several small pieces restricted to 

 the posterior half. Because of this close resemblance the writer 



-Analysis of Pscudocrinites abnormal is 

 n. sp. 



