1886.] NATURAL SCIENCES OP PHILADELPmA. *IB 



each arm joint, which inclose in the middle two rows of covering 

 plates, alternately arranged, of equal number with the side pieces. 



The dorsal cup is roofed over and covered by an integument of 

 comparatively heavy interradial plates of irregular arrangement, 

 which extend out some distance over the rays and enclose the 

 bases of the arms, but in no sense constitute or include covering 

 plates of the arms, as Angelin's figure (PI. xxv, fig. 15) clearly 

 shows. The plates at the margin of this integument meet and 

 connect with the incurved edges of the radials and peripheral 

 row of arm joints, which are proportionally much thicker than 

 those of other parts of the ray. The arms, with their covering 

 plates, which are laterally connected without the interposition of 

 interradlals or interaxillaries, emerge from underneath this 

 integument, which must have been pliant to admit of the varieties 

 of positions assumed. Also the summit plates oral and proxi- 

 mals must have been located beneath this integument, or we 

 could not understand their position and relation to the covering 

 pieces which are represented by Angelin's figure on PI. xvii, fig. 

 3 a. Only occasionally the first interradial is visible dorsally; 

 the dorsal cup, however, includes always a comparatively large 

 subquadrangular anal plate, which rests between the radials and 

 upon a hexagonal basal. This supports a very long, tapering, 

 lateral ventral tube, which rises between the arms. It is com- 

 posed of vertical rows of short, transverse pieces, and its walls 

 are pierced by numerous pores. 



The calyx plates appear to be united by syzygy, in part at 

 least, and the lines of junction are marked by pits and clefts 

 which penetrate deeply into the walls, as shown in fig. 4, PI. viii, 

 of Angelin, 



Column heavy, round, composed of thin joints, whose articular 

 faces are traversed by small radiating canals, which form pores 

 on the external surface. Axial canal large, pentangular. 



Geological Position, etc. Upper Silurian of Gothland and 

 England. 



These species have been described : 



1821. Crotalocrinus rugosus Miller, Cyathocrinus rugosus Nat. Hist. Crin., p. 

 Sy, pts. 1 A 4 B. 1808. Parkinson, Turban or Shropshire Encrinite, 

 Org. Rem., Vol. ii, p. 19.3, PI. 15, figs. 4, 5. 1837. Hisinger, Cyathocrinus 

 rugosus, Leth. Suec, p.89, Tab. xxv, fig. 3a; also Antekni, Heft iv, p. 217, 

 Tab. vii, fig. .3. 1839. Phillips, Cyathocrinus rugosus Phillips, apud 

 Murchison's Sil. Syst, p. 672, Tab. 18, fig. 1. 1843. Austin, Ann. and Mag. 



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