28 SMITHSONIAiSr INSTITUTION 



PLATE XI 



(All figures natural size except where otherwise stated) . 



^ PAGE 



Figs. i-io. Pycnosaccus scrobiculatus (Hisinger) 183 



Figs. 10,6. The type; after Hisinger, Leth. Suec, Supp. IT, pi. 39, figs. 4cr, b; lateral and basal views. 



Locality unknown. 



2a, b. Left anterior and posterior views of original of Angelin's pi. 15, fig. 10, and of his recon- 

 structed figure II. Xi- Course of nerve cords is indicated by ridges, the transverse 

 ridge showing the radial commisure. Klinteberg (/). 



3. Weathered specimen with obscure ridges and higher calyx; anterior view. Xt- 



Klinteberg (/). 



4,5. Two specimens from Klinteberg (/) ; posterior view X |, distal view X y- 



6a. Right anterior view of calyx, with IBr in place, — not an axillary. X 1. 



Klinteberg (/). 



66. Distal view of same. Shows IBr not axillary in both r. ant. and 1. ant. rays, proving that in 

 this species there may be more than one IBr. X 5. 



7. Large fragmentary specimen with calyx and arms. Shows 2 IBr in one ray and I in 

 another; surface markings and general proportions of calyx similar to those of the 

 others. Wisby (probably/). 



8a, b. Broken specimen probably of this species, with 2 IBr in some rays ; anterior and pos- 

 terior views. Natural size. Wisby (probably/). 



90, b. Right anterior and posterior views of specimen from Lau (/). It has very sharp surface 

 markings, but lacks the usual depression at angles of plates and the horizontal ridge 

 seen in other specimens. X I- 



gc. The distal edge of r. ant. R. and parts of adjoining RR; showing impressions of small 



perisomic plates in the interbrachial spaces between articular facets (o/). X 3- 



gd. Distal edge 'of anal x and parts of the adjoining RR, with similar impressions on anal plate, 



and on the shoulders of RR. X 2. 

 ID. Angelin's figure of P. costatus, much enlarged ; probably the young of this species. 

 Wenlock Gr. ; Silurian. Gotland, Sweden. 



All specimens in the Riks Museum, Stockholm. 



Figs. 11-16. Pycnosaccus nodulosus Angelin 184 



Figs, iia, 6. Right anterior and posterior views of type, original of Angelin's pi. 16, fig. 14. Com- 

 plete crown with part of stem ; abnormal in 1. post, ray which has no IBr, the other 

 four having a small, immature IBr under the axillary. X f- Follingbo (/). 



12. Specimen with l IBr in 1. ant. radius, 2 in ant., and an immature plate below axillary in 



I. post. ray. X *• Follingbo (/) . 



13. Specimen with I IBr in each ray. X I- Follingbo (/). 

 140, b. Small specimen having distinct ridges like P. scrobiculatus; distal view, natural size, 



posterior view Xf. Klinteberg (/). 



150. Broken specimen with stem, exposing inner side of two rays and part of tegmen. X !• 



Follingbo (/). 

 156. The rays and tegmen further enlarged, showing the ambulacra with extremely small 



covering plates, which can be seen also on the ventral side of the coiled arm. X 4- 

 16a, b, c. An abnormal specimen perhaps of this species. Has RA in primitive position in 



form of a radial ; anal .r much reduced and pushed partly above the line of radials ; 



anterior, posterior, and basal views. X I- Lau(/). 



Wenlock Gr. ; Silurian. Gotland, Sweden. 



All specimens in the Riks Museum, Stockholm. 



