ADDENDA et COERIGENDA. 



PL XV, figs. 7, 8, for Ogygia subduplicata read Phacops suhdwplicatus. 

 PL XVII, fig. 8, for O. pelatata read O. peltata. 



PL XX. The heading should be " Uppeemost Cambeian (Teemadoc)." 

 PL XXII, fig. 6, belongs to A. peltastes. 

 PL XXIII, fig. 6, description. Add: (Mr. Edgell's cabinet). 

 PL XXVIII, fig. 15, for J. cemula read I. cemulus. 



Page 129, line 3 from top, and^as5i»J, for antice read ante, and ioT posticc read ^one. 

 Page 130, after description of Ogygia angusiissima, add : " This may be but a sub-species of O. Buchii, 

 with a very narrow long axis. There is a more important var. common at Llandeilo, which has a wider, 

 shorter tail, and might be called var. convexa. It has only 11 lateral furrows to the tail; and is 

 characteristic apparently of the Lower, as O. Buchii proper is of the Upper beds of the Llandeilo Flags. 

 (Edgell)." Line 10, dele " Ogygia." It is surely a Phacops of the section Chasmops, as indicated ; 

 correct therefore the name on the plate. See above. 



Page 132, bottom. Add : Meadow Town, Shropshire : Cabinets of Mr. Morton of Liverpool, and of 

 Mr. H. Wyatt Edgell. See also page 160. 



Page 133, Ogygia scutatrix, also page 135, Ogygia peltata. I must amend these descriptions (p. 133 

 — 136), by referring PL XVII, figs. 9, 10, which from the width of the axis I had assigned to 0. scu- 

 tatrix, to O. peltata. In truth, they represent the $ form of the latter species, with which they occur 

 at "Whitesand Bay. A noble series, lately transmitted to me by Mr. Henry Hicks, show the distinctive 

 characters of O. peltata in both the broad (?) and narrow {^) forms. 



In the broader form the axis of thorax and tail is f ths the whole width ; and the fulcrum of 

 the thoracic rings, which our figure 8 (copied from the yet unpublished memoir on North "Wales by 

 Prof. Eamsay and myself) scarcely shows at all, is placed |ths out from the axis, and terminates a short 

 distinct facet upon the falcate tip, as shown in fig. 9. The tail has the axis reaching fths the whole 

 length ; and its width in one form is f ths, in another barely ith, of the whole width of the tail. The 8 

 or 9 cross furrows on the axis are only strong on the sides, leaving the central part only faintly ringed. 

 The side-furrows are like our figure, and have but faint intermediate lines or furrows. The fascia or 

 inner border is coarsely striate. 



Page 133, lines 9 and 12 from top, for axin read axem. Line 11 from top, for secondariis read 

 secundariis. 



Page 135, line 9 from top, for secondariis read secundariis. 



Page 134, bottom. Add : " Lowee Teemadoc," Carnarvon Eoad, 1^ mile west of Tremadoc 

 (Mr. Homfray). 



Pages 136 and 142, et passim, for brevispinoso read hrevi-spi/noso ; for retrocurvce read retro-curvce. 

 Page 143, line 8. Also Mr. H. W. Edgell's cabinet. 



Page 150, line 25. The labrura figured probably belongs to " A: peltastes " as a synonym for which 

 I should have quoted " Decade 2, Geol. Surv., pi. v, figs. 2, 4." They are reproduced in our PL XX, 

 which see. 



Page 153, line 29, dele " Abereiddy Bay," and insert Llampeter Pelfrey." Line 5 from bottom, for 

 ' cognota^ read ' cognita.' 



Page 154, line 19, for " Llandeilo Flags ?" read "Caradoc." Line 7 from bottom, for ' lasin" read 

 ' hasim.' 



Page 156, line 7, for " Shropshire" read 'Horderley ;' the species is local there. 

 Page 158, note. There has since been found reason to suppose the specimen quoted is really an 

 American one, not British. 



Page 162, line 22 from top, strike out ' cujus.' 



Page 164, line 8 from top, for ' cujus caput rottmdatum' read ' capite rotundato.' 



Page 168, line 12 from top, for ' Wrac' read ' Wrae.^ 



J. W. S. 

 March 12th, 1866. 



