30 SMITHSONIAN INSTITUTION 



PLATE XII 



(All figures natural size except where otherwise stated) 



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Figs. i-g. Pycnosaccus patei n. sp i86 



Fig. I. Mature specimen, not compressed ; left posterior view. Shows about the average characters 



of the calyx ridges, radial facets, one IBr, and arms ; distal ends of arms seen coiled 



in iBr spaces. The specimen was not quite vertically posed for drawing, and the calyx 



appears relatively too high. 

 20. Smaller specimen showing plated perisome in iBr spaces ; right anterior radial view. 



Natural size. 

 2b. Right posterior interradius, showing detail of perisome resting on shoulders of RR; parts 



of distal ends of arras also visible. X 2. 

 2c. Posterior view of same specimen, giving almost the correct relative proportion of the 



calyx; height to width about i : 1.5. 

 3a. Upper part of calyx, with arms, of specimen having interbrachial perisome intact in natural 



position. Note the sharp projecting nodes on some of the plates. Natural size. 

 36. Detail of iBr area of same. X 2. 

 4. Specimen with nearly complete stem. 



5a, b. Anterior and basal views of strong!)' marked specimen, slightly compressed vertically. 

 6, 7. Anterior and left posterior views of young and of mature specimen showing the general 



characters. The latter has an abnormal growth at posterior side, as if an anus through 



the calyx wall. 

 8. The largest specimen ; having ridges obscure, but showing the relatively small, angular 



arms. 

 ga, b. Anterior and posterior views of much eroded specimen from same beds at another 



locality ; without ridges, and with much more rounded arms than the preceding. 

 Niagaran (Brownsport) ; Silurian. Decaturville, Tennessee. 



All the specimens are from a bed of fine grained, shaly clay; and are in the author's 

 collection. 



Figs. lo-ii. Pycnosaccus bucephalus Bather (MS.) 187 



Fig. 100. A very mature specimen, slightly flattened ; posterior view. It has complete crown and 

 large part of stem; surface ridges broad and rounded; plates massive, and arms 

 heavy. British Museum, No. E562S. 

 10&. Anterior view of same, showing ridges somewhat plainer. 



II. Lateral view of a larger crushed specimen, with ridges more obscure; IBr displaced. 

 British Museum, No. E7427. 

 Wenlock Gr. ; Silurian. Dudley, England. 



