& 



6 OLAF HOLTEDAHL. [sEC. AFCT. EXP. FRAM 



We have not a few pieces from the heds mentioned above at Cape Gani- 

 perdown. Various sandstones are in evidence, red and grey, fine grained 

 and coarse grained. Some plainly exhibit ripple marks on the upper 

 surface. A microscopic section of a fine grained sandstone shows 

 somewhat rounded grains of le.ss than 0.5 m. m. in size, almost entirely 

 consisting (if (|uart/., with but a few grains of felspar. A rock of coarser 

 grain, showing grains as large as several ni. ni.s, contains much more 

 felspar, especially microcline. (See pi. 4. fig. 9). We also find a beautiful 

 piece of lime-conglomerate from the lower portion of the sedimentary 

 series. (See pi. 4, fig. 10). This shows pieces up to 1 dm in size, of a 

 grey limestone, extremely compaci in .some parts, lying in a lighter and 

 comparatively coarse crystalline matrix of calcile frequently also with 

 rjuartz grains. The pebbles in the main are rather flat or lenticular 

 As regards the flat pebbles the distribution shows an indication of 

 parallelism. 



The limestone in which the fossil remains were found in loose 

 pieces, is a very fine crystalline yellowish-grey rock. 



As regards the fossil remains themselves, they are deplorably frag- 

 mentary. We have some incomplete pieces of a quite small trilobite 

 form: some free cheeks, a very imperfect specimen of the central part 

 of the head shield and one incomplete pygidium. 



The specimens, of which some are represented in pi. 4 fig. 1 — 3, 

 belong indoubtedly to a Ptychoparia sp. but no exact identification 

 can be made with the above material. The specimens show a very 

 close coniformity with certain of the Ftyclioparia forms described by 

 Hall and Whitfield as Crepiceplial as from the Postdam Group in 

 Nevada, in "Geol. Exploration of the Fortieth Parallel". In the 

 form of both the cheek and of the pygidium the above form lies 

 very near P. anytiis (I. c. p. 219, pi. II, fig. 19- 21), and also 

 the two forms P. nitidns (p. iM2, pi. II, figs. 8, 10) and P. simulator 

 (p. 218, pi. II, figs. 16— 18), which Walcott in ,,The Paleontology 

 of the Eureka district" p. 57, combines into one form, P. nitidus 

 Hall and Whitfield. The central portion of the head shield exhibits 

 some diviation from that of the forms above mentioned. It has a 

 narrower frontal limb, and also the facial sutures diverge less markedly. 

 As regards the central portion of the cephalon, this agrees better with 

 that ol P. ti)usHlc(Uii..s, shown in "(ieol. Expl. of the Forth. Par." pi. II, 

 fig. 22. 



